Aurio said:
I rule that they get teleported somewhere else after being used. That explains why they still exist and keeps things balanced.
ummm the become normal books after being read.
From the SRD:
{quote]Tome of Clear Thought: This heavy book contains instruction on improving memory and logic, but entwined within the words is a powerful magical effect. If anyone reads this book, which takes a total of 48 hours over a minimum of six days, she gains an inherent bonus of from +1 to +5 (depending on the type of tome) to her Intelligence score.
Once the book is read, the magic disappears from the pages and it becomes a normal book. Because the tome of clear thought provides an inherent bonus, the reader will earn extra skill points when she attains a new level.
Strong evocation (if miracle is used); CL 17th; Craft Wondrous Item, miracle or wish; Price 27,500 gp (+1), 55,000 gp (+2), 82,500 gp (+3), 110,000 gp (+4), 137,500 gp (+5); Cost 1,250 gp + 5,100 XP (+1), 2,500 gp + 10,200 XP (+2), 3,750 gp + 15,300 XP (+3), 5,000 gp + 20,400 XP (+4), 6,250 gp + 25,500 XP (+5); Weight 5 lb.[/quote]