An excellent translation of the seminal Indian Madhyamaka work "Four Hundred Stanzas" of Aryadeva, who is traditionally considered to have been a student or disciple of Nagarjuna. This volume also includes a complete and extensive commentary by Gyeltsap, the second heart disciple of Je Tsong Khapa. Gyeltsap's commentary is closely modeled on Chandrakirti's Sanskrit commentary.
As with most verse works of the period, the root text is extremely cryptic, and likely could not be translated into coherent English independent of a commentarial text. Gyeltsap no doubt differs from Chandrakiri in his use of Dharmakirti's technical vocabulary to explicate conventional existence, but I believe that he follows Chandrakirti closely in understanding the meaning of the verses.
The first two hundred verses give a preliminary account of practices such as abandoning pride and the belief in the purity (read: desirability) of mundane phenomenon. The last two hundred verses offer an refutation of concepts of ultimate existence following the model of Nagarjuna.
Geshe Sonam Rinchen offers a short commentary of his own on the first half of the volume, explaining basic concepts of Buddhist practice in a clear, persuasive style.
I believe the commentary was necessary because it's a bit difficult for modern audiences from any background to make contact with the existential dimension of Aryadeva's teachings. Unlike Shantideva's Guide or Nagarjuna's Precious Garland, his practice instructions are rather abstruse.
Likewise, with respect to the analysis of ultimate existence, personally I find Nagarjuna's work rather more clear. I've read a fair amount of Buddhist philosophy, but Aryadeva left me somewhat baffled several times. His approach is not particularly systematic, and the basic sense of what he's trying to say is often rather obscure. The commentary helps often, but not always.
This is an important translation of not one but two works of major historical significance in the history of Buddhism.