Young Stalin is currently on sale at Amazon at the price of £4.99 (for the paperback version).
This book is the prequel to Stalin: The Court of the Red Tsar
What is particularly compelling about this biography is that it flies in the face of the "boogie man" view of history (which is so beloved of the current US administration). Of course Stalin was an evil and degenerate despot - but any attempt to understand how a man like that could rise to power at the time that he did has to go beyond a dull witted good versus evil view of history. And that's what this book manages - you almost end up liking the young Stalin - his force of personality, his charisma and his sense of adventure.
It's a cracking book.