Save the game, then purchase a Specialization Book from a vendor. The message "Specialization Unlocked" will appear. Load your saved game file. You will have regained the gold you spent for the book, but the specialization will still be unlocked.

When you first get to your party camp, you will see Bodahn Fennick, the Dwarf trader. Speak to him and check his wares. Looking through, you will see the two specialization books, Ranger and Templar. Save the game, then buy one. It will unlock that specialty. Reload your game and buy the other one. You will now have both specialties unlocked and still retain your gold after reloading your game twice. This works every specialty book.