This is an article that shouldn't need to be written, but sadly it does. There are sharks out there, but thankfully most of them are amateurs and shunned by the professional trade. This is by no means endemic. It should also be noted that these issues have been around as long as the trade and will continue. We seek only to give attention to the matter.

Every collector has their own opinion on what constitutes a good addition to their collection. Some collectors want everything fine and inscribed, others couldn't care if the jacket's present or not, others want everything in full morocco with five raised bands, clamshell and the page edges dyed with the book dealer's blood. What every collector wants though is transparency. They want to know what they're buying. Here is an outline of things you should bear in mind when making a purchase.

This isn't a list of condition points, we might do that another time, though it will be touched on briefly.

Authenticity

The first and arguably most important consideration is inauthentic signatures. I have never met a collector who doesn't care if a signature is authentic or not. I have a book next to me bearing an inscription from Virgil Finlay. I have no reason to doubt its authenticity, so neither should you. That sounds like a great line from a used car salesman, but the point is that a buyer should be able to rely on a dealer to have adequately assessed a signature. The diligent dealer will do the following:

1. Examine the physical appearance of the signature for undue hesitation, odd strokes and other tell-tale signs. 
2. Compare the signature to records of other sales from reliable sources. 
3. Examine the provenance of the book and signature; is the story behind it backed up with physical evidence? I had a story from a seller once that was very detailed and all checked out, but there was no evidence of it having not been fabricated - the signature was a forgery.
4. Consider the contemporariness of the signature; many signatures change over time.
5. Consider the situation surrounding the signature. Was Hemingway in Venice when that book was signed?

To build trust with a dealer you should do these things yourself, particularly in the early days of a relationship (professional relationship, I should add; we don't offer those type of services; not regularly at least). If things start to look a little odd, they probably are. Contact the dealer and bring it to their attention; they will either be able to tell you why they've deemed it authentic or accept their mistake. 

Take note also of the experts in the field. Come to me for Philip K. Dick signatures, Terry Pratchett, Stephen King and plenty of others. You can come to me for T.S. Eliot or Graham Greene authentications but I won't authenticate them personally, I'll have a colleague do it who is an expert in the area.

Disclosure of Condition Points

The complaint we hear about other dealers most is mismatches of condition. We're not immune to it ourselves. We've missed things in description, never purposefully, but it does happen. We've also had disagreements on grading. This is inevitable as these things are often subjective. My mild foxing is another's moderate foxing. Even the camera gets the colours wrong sometimes. A collector will encounter this at some point, and the dealer should always make it right. If it becomes a trend though one has to approach with caution. 

Restoration

We don't sell restored books, it's not elitism, it's simply that we don't like the look of them. It is something though that is prevalent in the trade. That's not to suggest it's a bad thing, good restoration (and conservation) work is an art form and should be celebrated. We all conserve when we put jacket protectors on and I imagine we've all cleaned a little dirt off a glossy jacket. At the other end there are jackets that have had 40% of the loss restored and look better for it, bindings that have been tightened up, books that have been rebacked. This is all valuable work and retains the books for the future. However, it MUST be mentioned in the description, and clearly. Blowing the dust off the page block is just common sense, spraying red over the pink needs to be disclosed.

Marriages

If ever there was a contentious point in the trade is was marriages. A marriage is where a book and its dust jacket are brought together to increase the chances of a book being sold (and usually increasing the price). Some members of the trade frown on it, others do it as a matter of course. Many think it's fine as long as it's disclosed. It is common to state that the jacket has been supplied. It's down to the buyer whether they care about this. Sometimes it's obvious, particularly where fading has occurred and the patches don't match between book and jacket. Sometimes it is impossible to tell. If it's an issue for you, make that known to the dealer. Often, jackets can be salvaged from ex-library copies where they've been protected since day one. If this bothers you, you need to understand your dealer's policy.

Sophistication

This is up there with forgery as one of the things that is unacceptable (where not described). A sophisticated book is one that has been doctored to make it more desirable. Arguably, marriages are a form of sophistication, but I'm not sure that I know anyone who'd put it in the same category as a fully fixed-up book. To explain what sophistication is here are a few examples:

1. Tipped-in signature sheets; find a signed copy of a common book, pull the page out and get your binder to tip it into a rarer book. This is usually quite obvious, but sometimes can be difficult, if not impossible, to tell.
2. Tipped-in publication information; again, this can be difficult to spot. Most often it's a case of finding a first impression of a book that matches the second impression in most of the physical description. Get a decent copy of the second impression and a crappy copy of the first impression, take the copyright page from the crappy copy and tip it into the nice impression.
3. Replacement boards; this involves removing the entire page block from a book and putting it in better boards.
4. Fix-ups; basically hacking a book together. sticking entire signatures (i.e. a sheet folded in pages) into a book, replacing endpapers.
5. Removal of ownership; this is the most common. Collectors hate library copies, so sometimes (amateur) dealers take it upon themselves to alleviate the world of that hatred by removing all traces. Again, it's usually obvious:
   • Thinned paper where a stamp has been sanded off
   • Bright page edges where stamps have been sanded off, and one would expect a little dust
   • New endpapers to remove trace of stamps
   • Scuffs where a label has been removed - this is very common
   • Bookplates stuck in odd places to cover thinning or stamps.

Frankly, I don't know who has the time, desire or audacity to do this, but it does happen. Actually, I do know, I'm just not saying here!

Edition

This is obvious - make sure you're getting the edition you expected, and impression, and issue and state. Sometimes issue points aren't commonly known and a book can look like the first possible state, but in fact be much later. Dealers might not have access to this information either, but a good dealer will do their research and also make it right if they make a mistake. The buyer should research too, but ultimately they need to be able to rely on their dealer.

Who Owns the Book?

This is a weird one, and not common but sometimes (crappy) dealers will pass a book off as theirs that they don't own. This is actually pretty stupid. It's a good business plan - sell the book, get a discount from the owner, and you've got easy money. It's stupid because it's bloody obvious. Look for inconsistent photographs, do a Google image search to see where else that image can be found, look in auction records, ask the dealer if they own it. It's unprofessional too because the middleman has not actually catalogued the book themselves so doesn't know what they're selling.

The silliest example of this I've seen recently was with a dealer who, in the space of a few months, suggested that they had four books for sale, each likely exceeding $100,000 - one likely $1,000,000. Details were never forthcoming. It's a bit of a scam, but not a particularly good one.

Print on Demand

A shaky one here - basically books printed to look identical to the first edition. Very uncommon, so much so that it's contested, but the ones I've seen are clearly printed on demand.

Don't be Fooled by the Price Tag

It's easy to think that nobody would mess with an expensive, rare book. The opposite is true, nobody would bother too with a cheap book.

Nota Bene

Thankfully, this is the exception and not the rule. 99% of the books out there will not have been doctored, poorly described or bastardised in anyway. And fortunately, the 1% aren't distributed evenly across the trade. You'll know it when you see it.

If in doubt, ask a dealer you trust.