Hey!

To my knowledge, there is no book that'll provide you with a detailed discussion of the Sanada Ten Braves. There are passages in more general histories - wiki references Joel Levy's Ninja: The Shadow Warrior though I've never come across it. Historically they are a construct of Sanada Yukimura/Nobushige's descendant in the late 17th century in an untranslated book called Sanada Sandaiki - though there are ninja clans attested in Kai/Shinano (the Sanada heartlands) their exact identities are, unsurprisingly, not widely known. It is believed that during the Osaka Campaign Yukimura had ~50 ninja under his command (Turnbull, Osaka 1615, Osprey Publishing) but details beyond that are - as far as I know - not known.

My understanding of Japanese history - particularly for the Sengoku/Azuchi Momoyama period - is built on Osprey's books on the key campaigns of the era, and by extension anything by Stephen Turnbull who's incredibly prolific, though he is primarily concerned with matters military. I must profess to general ignorance of the rest of Japanese history beyond wikipedia though.