I’ve studied Zen for years, and while I agree with your recap of Shambala, I feel that American Buddhism has an elitism problem, which I am well familiar with and loathe, that tends to steer newbies away from genuinely accessible teachings. Throwing the Lotus Sutra at people who barely understand what the Four Noble Truths or the Eightfold Path are is a good way to make them feel alienated from the path, but I’ve seen it done.
There are certainly a lot of accessible works out there, esp. from Pema Chodron and Thitch Nhat Hanh and the HH Dali Lama himself. But the reason I always throw “Shambala” at people is that it is less about “jump into the deep end and here is Theravada and Mahayana and…and…” and more about some very basic principles that challenge Western-centric religious philosophy, which is where a lot of people come from.
Sure, the Tipitaka and the Dhammapada are fantastic texts, but I respectfully disagree that they are accessible for people unfamiliar with the basic principles of Buddhism.
(If anyone reading along is interested in my recommendation for a book that covers “Buddhism 101” well, I suggest “The Heart of the Buddha’s Teaching” by Thitch Nhat Hanh.)