I really like him. Is there anything I should know before I read more of his books?
You could do worse than reading his stuff.
I have to admit, I am not a huge fan of his. I think he has a drastic tendency to oversimplify, and to teach/preach down to his audience, and I feel like he kind of cheapens Hasidic and Kabbalisitic teachings by presenting them couched in or framed by self-help pop psychology. I also think he is just using a few dabs of Hasidut and Kabbalah as a crunchy coating for an interior of
kiruv (outreach to non-Orthodox Jews to get them to become Orthodox) of a relatively classic model.
That said, we live in a time when the teachings of Kabbalah and Hasidut (to a lesser extent) have become frequent tools for hucksters, con artists, and the worst kind of
apikorsim (heretics), and Aaron's none of those. He seems like a fairly par for the course Orthodox
shaliach (one who does outreach), which means that he seems to have genuinely decent intentions, and he actually seems to know something, even if he doesn't always share it with you.
At best, his stuff seems to have one or two useful tips for helping to relate spiritually to the holidays and mitzvot. At worst, it's feel-good fluff.
But as far as I can tell, it's harmless, and so is he.