Salguero's work has good clear color photographs --- most others are in B&W.

He makes interesting correspondence between the assisted-yoga TYM stretches, and their actual Yogic names/applications;
however has nowhere near the amount of scholarly historical background and exposition as found in Brust (aka> Asokananda).

If you are like me, you'll get anything you can on the subject. Each book has a few things the others lack. I've found public libraries often have useful TYM works. I'd find works no longer available to buy, so I'd photocopy or scan them.