BACH: Music in the Castle of Heaven. By John Eliot Gardiner. Knopf. 672 pages. $35.

Who better than the inimitable Sir John Eliot Gardiner to write a biography about Bach?

Gardiner, one of the best-ever interpreters of baroque music and a lifelong Bach enthusiast, has spent his entire career as a conductor collecting material for this magisterial tome.

It's not a biography in the traditional sense, for that, you might consider "Johann Sebastian Bach: The Learned Musician" by Christoph Wolff. This is a hybrid of sorts, a mix-up of intellectual biography and musical analysis.

Since we know only a little about Bach's life and thinking (primary sources are few and the historical record is a bit sketchy), Gardiner has decided to figure things out by taking a hard look at the music, especially the great choral masterworks. These, he has concluded, shed the most light on Bach's potential character because they contain words and meaning, because they help contextualize the master composer within his time period and religious tradition.

It was a good idea, even if Gardiner might occasionally be accused of stretching things a bit, or giving short shrift to the secular stuff.

He paints a picture of Bach as a young rebel, which maybe he was and maybe he wasn't. And he doesn't skimp on information about Bach's financial and artistic struggles. But the best parts of this admirable and admiring book are those passages that only Gardiner could write, those intense insights he brings to the table.

It is clear that Bach's passions are shared by the author, who is mostly writing for readers who also are passionate about the intricacies of this sublime music and the miracle of this master composer who left us such a timeless treasure trove.

What a marvelous addition to the canon.

Reviewer Adam Parker is arts writer and book page editor for The Post and Courier.