I just wanted to point out that there is a good explanation of SSTables B-trees and other database structures in a whoke chapter of the great book Designing Data-Intensive Applications, by Martin Klepmann.
In the middle of this book right now, specifically the unreliable clocks part. The explanations have the right amount of depth. It's a great read in so far.
not to mention, some awesome references at the end of each chapter. I had made it a point after each chapter to randomly pick an interesting reference and read that as well.
I just ordered the book from your recommendation, thanks.
I also discovered it on Hacker News, hope you'll enjoy it!