I'm now wishing I had a Core rulebook without the magic items, to save on weight.
Once I started investing in PDF copies of the core books and got used to not having physical pages to turn or stick a bookmark, I swiftly got hooked on using e-books for everything. Now instead of a crate of books to tote to games or to take up space on the game table, I have a smartphone with all my PDFs on it for GM use. Here are my recommendations:
1) Get the PDF version of everything you want to use as GM. I still have, and will keep, the "core" physical game books I still have but they are for the players to use. I've upgraded.
The PDF version of any PF book is cheaper than the printed version (as far as I know) and as long as you retain your account on Paizo's website, you will always be able to re-download it in case your offline copy is destroyed or deleted
2) Get a good PDF reader. Either Adobe or Foxit will do. PDF readers for PCs and Macs are everywhere, but Adobe also has a Droid version of their reader that will run on Droid tablets and smartphones too. I just think it is so cool to look up any rule, monster, spell, etc. on my phone anywhere I fancy, without needing to go to my hardcover copies.
3) Learn how to use the bookmarks in the reader. Navigating the list of bookmarks on a given file is so much easier than navigating to the page number you *think* you might need (or going to the index or Table of Contents first, and then looking up the page you need). At worst, the bookmark will take you to the right page and then you have to play with the zoom setting if it is not to your liking. But much better than flipping pages or waiting for that player who hogs your books every session to bother giving it back.
4) Learn how to open multiple windows in the reader. (I know the PC versions of Adobe Reader and Foxit both do this...not sure about others.) You can keep the book "open" at multiple pages without having to flip back and forth...instead you switch between the different Adobe windows on your computer.
5) Your e-books will never get stains or stink of cigarettes. Always a plus for me...
Downside: can't hand them over to players to look stuff up without letting them also handle your smartphone/laptop/tablet/whatever. But then, they should be buying and using their own copies anyway.