Hey there! good question…
Here’s a short but hopefully fruitful list:
- The OG 13th edition is available online
- You can find the Aristotle SC Grail
- The Magoosh Idiom e-book can be found
- GMAT Club has some great question banks:
- This page has links to many question banks, among them 700–800 level problems and solutions, a file with 1000 problems, and another one, and a Free Test bank (to download you’ll have to register to the site).
- examPAL has a lot of free material – lessons, practice questions and explanations. They also have a book, partially written by yours truly and costing 1$, about sentence correction basics.
- A whole lot of free GMAT material someone uploaded
Important Note: some of the items listed may be under copyright infringement and thus I don’t actually recommend downloading. Here are links where you can purchase them:
- OG 13th edition
- Aristotle SC Grail
- Magoosh Idiom e-book
That’s my answer in a nutshell, but I’d be happy to go further into it with you and answer any follow-up questions you may have. Talk to me here (in the chat bubble in the bottom-right corner). Waiting to hear from you!