Identifying
Telling a Franklin Library from an Easton Press across a room.
Both are American, both leather, both gilt. Collectors mix them up constantly, and the difference matters to price.
The covers are the quickest tell. Franklin Library runs to dense allover gilt tooling covering most of the board, ornate from a distance. Easton Press is more restrained, with the decoration concentrated on a spine carrying raised bands.
Inside, both use gilded edges and patterned endpapers, so that is no help. The accompanying material is. Easton Press volumes commonly came with a separate notes leaflet, and their signed editions carry the signature on a bound-in page rather than a tipped-in slip. Franklin's Signed First Edition Society volumes are signed by living authors, and that is where the value concentrates.
The publisher is only the first question. The second is whether it is signed, and the third is whether it has ever been read. Both houses produced a great many volumes, and unread condition does most of the work in what a copy is worth.
Collecting
What the limitation leaf actually tells you.
The page that says "this is number 47 of 300" does more work than most buyers realise.
It fixes the size of the edition, which is what scarcity is measured against. It usually names the states, and the states are not equal: a press issuing lettered, numbered and artist copies is issuing three different books at three different prices, and the lettered run is normally smallest and most sought after.
It often carries the signatures too, which makes it the point of authentication for the whole volume. A book missing its limitation leaf has lost its proof, and a large part of its value, however good the rest of the copy looks.
So when buying at distance, that is the page to ask for a photograph of. Not the spine, not the slipcase. Any honest listing already has it.
Construction
Why a sewn binding outlives a glued one.
It is the single structural difference that decides whether a book is still usable in a century.
A sewn book is built from folded gatherings stitched through the fold and attached to the covers. The thread holds the block together and the pages open flat, because nothing is fighting the hinge. Adhesive is present, but it is not doing the work.
A perfect bound book has its pages cut flat at the spine and held by glue alone. Quick, cheap, fine for a while. Then the adhesive hardens, the spine cracks where it has been forced open, and pages come away in blocks.
Open a book you are thinking of buying at the middle and look down into the gutter. If you can see thread, it was built to last.