I am a tightwad. I do not like spending a lot of money on things (with a few notable exceptions). Even though my passion for reading is overwhelming, this still applies to books. I hate spending money on books that I could get for much less or free in a couple years. Because of this, I've come up with a few excellent strategies to find said books for cheap, which means that my bookshelves runneth over often.
I share with friends
When we were in school, Maddy would borrow ARCs from me and I would pillage through her room and borrow dozens of books from her. An easy way to save money!
I borrow from the library
Easy enough, right? Well here's a confession... I'm not actually allowed to borrow from the library any more. They cut me off because I had more than $50 in late fees. Well, that's a lot of money! I should pay them back some day, but I sort of figured in my mind that volunteering there for four years sort of makes up for it. Regardless, I have come into possession of my mom's library card and discovered that my library is connected to a digital library service where I can check out ebooks and audiobooks online. The best part? The books auto-return so I never get late fees!
I shop at garage sales
Believe it or not, a lot of people ditch their old books at garage sales, and sometimes you can come across great finds! Also, if it's the end of the day, people will start giving stuff away for free so that they don't have to take the time to dispose of it later. I've gotten a couple giant boxes of books for free this way.
I shop at library sales
There was this giant library sale in Eugene where the books were $.50 or $1... what a deal! They often had newer books as well. I haven't found anything the same in my hometown, but I'm sure I'll stumble across something soon!
I shop at Goodwill
I find tons of great finds at goodwill for about $2-3. I've found some really recent novels as well as some of the classics that I'm always looking to add to my collection!