I just bought some nice e-books on sale from Forward Chess. They have a number of interesting titles at big reductions.
These e-books have game viewers (so you can play through the games) and Stockfish engine (so you can examine variations and evaluations).
I got:
Famous book "Life and Games of Mikhail Tal" ($9.99), as my old low-quality Batsford paperback fell apart on first reading years ago;
"The Livonian Knight: Selected games of Alvis Vitolinsh" ($4.99). I am a fan of Vitolinsh and many such less-known tactical wizards.
Can also recommend Vol. 1 of Andrey Terekhov's Vassily Smyslov biography, which I already own in physical form.
I'm also seriously considering the (physical, from Thinkers Publishing) book "Forgotten Genius: Life and Games of Albin Planinc". Planinc was a spectacular tactician who had mental problems and a short career. But the book is too pricey :-(