Can't you just print that for free from the internet, though, a corner of my memory asked . . . ?
Not quite, it turns out . . .
A previous version of the book is currently still available here (large pdf), titled this time as Secret Matches: The Unknown Training Games of Mikhail Botvinnik. It's edited by Hanon W. Russell - but with many games annotated by Timman, and with a very interesting essay by him too at the start, about the theoretical importance of the games. But on the other hand, this seems to be a new addition to the commercial version of the book:
The book also has an amazing chapter by Yuri Averbakh, one of Botvinnik's training opponents. Averbakh relates how he had to play in front of a blaring radio because Botvinnik wanted to steel his nerves against noisy disturbances. "After five hours of play", writes Averbakh, "I felt like an utter zombie."I always feel like an utter zombie after five hours of play, but team-mates from our club will know that already. Anyway - if I were you, Streatham & Brixton Chess Club, I'd download the free version now, in case it disappears like a secret.