(I note there is a "one dharma" retreat at Buddhist Insight retreat center which will be lead by a Tendai leader. This is Japanese Tendai, not Chinese Tendai.)
It's an old idea, there is only one dharma. So how do you account for all the different traditions and different practices? So far the execution of the book has been OK.
In other news, Mastering the Addicted Brain is by a Thai-American who writes about the importance of meditation. It's very concise, practical and comprehensive. An ideal book for someone new to recovery, and anyone who wants to brush up on recovery principles and ways.