We sometimes get questions around the differences between the Old-School Essentials tomes and box sets. The fundamental difference, of course, is that the tomes present the game in a single book (or a pair of books, for Old-School Essentials Advanced Fantasy) where the box sets divide the game into a set of slim books (each detailing a certain topic). There's a basic overview of the different versions of the game on the About Old-School Essentials page.

There are, however, also some subtle differences that we thought it would be useful to list.

Classic Fantasy

No differences. The Classic Fantasy Rules Tome contains exactly the same content as the Classic Game Set.

Advanced Fantasy

There are a few small differences between the Advanced Fantasy Tomes and the Classic + Advanced box sets. These small differences are due to layout and manufacturing constraints — each book must be a multiple of 8 pages, so some very small cuts were required in certain cases.

• Advanced class level titles: The Advanced Fantasy Player's Tome lists suggested titles for characters of certain levels, including all Classic and Advanced classes. The Advanced Fantasy Characters box set book does not list level titles for the new classes introduced.
• High-level play: The Classic Fantasy Characters box set book includes very rough guidelines for extending play up to 36th level for human character. (These guidelines can be viewed on the SRD.) The Advanced Fantasy Player's Tome does not include these guidelines.
• Dogs: The Advanced Fantasy Player's Tome includes two kinds of dogs that characters can purchase (war dogs and hunting dogs). The Advanced Fantasy Characters box set book does not include dogs for purchase. Dog stat blocks are, however, present in both the Advanced Fantasy Referee's Tome and the Advanced Fantasy Monsters box set book, along with prices.
• NPC adventuring parties: The tables for generating NPC adventuring parties in the Advanced Fantasy Referee's Tome include all Classic and Advanced classes. The equivalent tables in the box sets only include Classic classes.