Probably the most iconic cover of the early D&D days, the AD&D Player’s Handbook was probably the book most players would have looked at  and used the most. After all it’s really the only one that most players need to have, the other core books like the earlier released Monster Manual and the upcoming Dungeon Master Guide were for the DMs eyes particularly and the adventure modules would be exclusively for the DM. If you were just a player, which something like 5 out of 6 players would be, this was all you needed.

As a book it is a vast improvement over the original D&D and it’s a much more complete system than what could be found in the Holmes’ Basic Set. This brings together all of the stuff that was previously spread among a bunch of different manuals, supplements, Strategic Review and Dragon issues into a coherent volume that also editorializes much of that. All that weird psionic stuff is stuck in the appendices as optional rules, for example.

For the modern reader this is a much more recognizable system than what was in the original D&D or even the basic set, overly complicated and with some nitpicky rules particularly when it comes to turn order and attack/casting speeds, it is however very much D&D as we know it, particularly if you played it at any time before 4th edition (I started in 2nd myself, for example). Much of the book is taken up by spell lists and rules, and that’s something that still happens, but if you are at all interested in seeing where D&D comes from, it’s definitely worth a read.