I tab my most used gaming books by chapter, and then again across the top edge with frequently used pages. It is much more useful than a book without tabs, and helps me keep track of my books even if I do pass them across the table. When you consider how many times you need to open the book to look something up, those tabs pay for themselves in a hurry.
I also insert the errata in my books. Small bits are done by hand, while larger corrections involve using scotch tape and closely trimmed paragraphs to be inserted as necessary. It's a good system overall, not to mention I am better informed about differences between 1st and 2nd printings, and can tell people what they are missing (or not).
The work that goes into updating and tabbing my books make them worth more than new books to me. The payoff is less time flipping pages, and a greater comfort factor when it comes to knowing my books inside and out.