David Brown (a British musicologist) has a highly-praised 4-volume study of Tchaikovsky, which puts the emphasis on the music. It was exceptionally complete, but rather specialized for my own level of interest and understanding, and I confess to having done a lot of skimming of my library copies.
Brown has published (in the UK) a one-volume study,
Tchaikovsky: the Man and Music, but I don't think it is published in the US at this time.
More directly related to our interest here, there's
Tchaikovsky's Ballets by John Wiley.