Spock Must Die is a good read, but I don't see how or why it would be appealing to non-Trek fans.
The Entropy Effect is my favorite Trek novel, I've read it several times and I love it more every time.
Planet of Judgment wasn't all that great, mostly because I found the aliens annoying.
My Enemy, My Ally is great, as is the rest of the Rihannsu series.
The First Adventure was fun too, even though it wasn't quite the crew we're used to.
I haven't read the rest. I tried How Much For Just The Planet but I didn't like it.