I have come to like Wayne Grudem's Systematic theology for helping people with basic questions like this. It doesn't have the depth of an entire book on one subject, but it has chapters on most major subjects Christians ask about or debate about ( with the notable exception of the sabbath controversies).
I think he is historic premil but he lays out all the positions very well...even as an amil

I'd suggest it as a good basic primer. I know many many Reformed folks who disagree with Grudem on baptism ( he is credo) and gifts ( he is a continuist) but prize his book as one of the best general references available.