That's a great question, M!
The transition to digital tests is definitely something that you will want to familiarize yourself with. The
LSAC website provides 3 digital practice tests (PrepTest 71, 73, & 74) and I would recommend that you take all of them.
As to whether to purchase ebook or paper versions of additional practice tests, that's somewhat based on your personal preference. The ebook versions will not be in the same format as the digital test so it won't be approximating the actual digital test-taking experience. However, it may help just to get accustomed to reading LSAT questions on a tablet and practice digital highlighting.
Whether you go with the ebook or the paper versions, the most important thing is to try to approximate what the digital test will be like as best as possible. The main difference you are likely to encounter when taking the digital LSAT is that you will not have as much flexibility in terms of how you mark up text. You will be able to underline text as well as use 3 different colors of highlighters. So whether you use the ebooks or the paper versions of practice tests, get used to marking up passages using only underlining and highlighting. The digital version will allow you to cross off answer choices (so you'll still be able to eliminate those losers!) and flag questions that you want to come back to. You will be provided with scratch paper and a pen so you can take notes, draw out conditional diagrams, etc. so even if you use the paper tests, I'd recommend using scratch paper instead of marking up the actual test booklet.
Good luck on your retake!
Best,
Kelsey