Lord of the Rings,
Unfinished Tales and
The Silmarillion. Again ...and not just the second time, either. Hardly.
What can I say? Like a good movie, Tolkien can be read over and over. LOTS of details that make it virtually new each time.
I had started a JavaScript book, but with no real application for what I learn, retaining the knowledge I gain (in a vacuum, as it were) becomes problemmatic.