If you’re interested in the technical aspects of radio, and you have some electronics or technical background, I can’t recommend The ARRL Handbook enough. I actually have the 2011 edition. I’ve read complaints that the new handbook doesn’t teach enough about analog electronics. That may be the case for folks with a deep understanding, but for us rf noobs, it’s plenty rich. If you’re new to electronics, the first few chapters are like a crash course in electronics theory. The next few chapters do a deep dive (by my standards) into all aspects of RF electronics. So instead of building things, I’ve been trying to plow through some heavy reading to get up to speed.