Out of print and with used copies now costing over $70 on Amazon, The Official Preppy Handbook is available to read online, for free.
It’s very readable on archive.org. You do need a (free) account to “borrow” a copy, but creating an account only requires an email address. You can use a throwaway if you want.
Read The Official Preppy Handbook on Archive.org
You do not need an account to read it on Issuu, but the viewer may be difficult on some devices:
Read The Official Preppy Handbook on Issuu
As you surely know, the Official Preppy Handbook is what brought prep style to the masses in the 80’s. Originally written as satire (by legitimate preps), it became an instant hit and was often read unironically.
Check out this 1981 New York Times article discussing the origins of the book. Another quick and interesting read is this Garden and Gun article with a few anecdotes about prep in the South.