Have not read it, but I plan on ordering it eventually.
I have read bits of Tai Situ Rinpoche's other recent volumes, which are really transcripts of teachings he's given in the context of various large empowerment groups--Kagyu Ngakdzo, etc. They are all good, and worth reading--if you're interested in the material, as it is specific to the topic. They're nice volumes--the ones I've seen.
For the Shangpa volume, my understanding is that these are transcripts of teachings given on the occasion of the bestowal of the Shangpa KaWang that was given at the request of Yangsi Kalu Rinpoche a few years back. There's limited info available on the web, regarding a table of contents, etc., so it's hard to say exactly what's included, but I'd bet there's a great deal of background information regarding the history of the lineage, major figures, and main practices--but I'd doubt the actual practice instructions would be included in any detail.
If you're interested specifically in the Shangpa lineage, I can recommend the following books:
Timeless Rapture is the best volume out there on the lives, and songs, of the Shangpa lineage masters.
Jamgon Kongtrul's Retreat Manual gives up quite a bit of info about the practices of the lineage themselves, though it's not only about the Shangpa lineage.
Luminous Mind by Kyabje Kalu Rinpoche covers the Shangpa lineage, as well as more general information about Buddhism in general and Vajrayana in particular. His other books, particularly Secret Buddhism, also have quite a few nuggets of information.
Like an Illusion contains some abridged life stories of the Masters, and some information about the lineage and practices as well. I wish that it were not abridged.
There are some other sources, as well......