You've been given some excellent recommendations here, including the caution about Keith Dowman's translations, certainly enough to keep you occupied for quite some time. Offhand, I'd also suggest a pair of books by Tsoknyi Rinpoche, another of Tulku Urgyen's brilliant sons--"Carefree Dignity" and "Fearless Simplicity". Both of these were compiled from talks he's given and capture the flavor of his engaging teaching style.
"All the sublime teachings, so profound--to throw away one and then grab yet another will not bear even a single fruit. Persevere, therefore, in simply one."
--Dudjom Rinpoche, "Nectar for the Hearts of Fortunate Disciples. Song No. 8"