I haven't read his history of the revolution though I am curious if it's any good (I would read as a critic and not as a reader seeking information, obviously).
When you're familiar with that, Dmitri Volkogonov's biography of Lenin is probably a good next step for him. Radzinsky's biography of Stalin is the best I've read so far. I'm not sure that any good biography of Trotsky has been written in the West - they treat him like some sort of Che Guevara, with a heroic patina liberally applied to a wretched person and life. I guess Volkogonov's superficial bio is acceptable.
https://www.amazon.com/Lenin-Dmitri-Volkogonov-ebook/dp/B003DYGNMY/ref=sr_1_4?ie=UTF8&qid=1489531523&sr=8-4&keywords=Volkogonov
https://www.amazon.com/Stalin-depth-Biography-Explosive-Documents-ebook/dp/B003F3PMNO/ref=sr_1_1?s=digital-text&ie=UTF8&qid=1489531550&sr=1-1&keywords=Radzinsky+stalin
https://www.amazon.com/Trotsky-Eternal-Revolutionary-Dmitri-Volkogonov/dp/0684822938/ref=sr_1_1?ie=UTF8&qid=1489532034&sr=8-1&keywords=Trotsky+Volkogonov
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*