For the purposes of learning antenna theory at the level of Balanis's 'Antenna Theory', I think Jackson is severely overkill. It's also written for physicists rather than engineers, so the emphasis is different. On the other hand, Jackson's problems are quite excellent. There's all kinds of interesting stuff in there that is hard to find in most other places (plasma physics and MHD come to mind). Something like Griffiths or Cheng will be just right. I studied Computer Engineering in undergrad, and worked through several books on electrodynamics at the time (and did several courses in EM), including Jackson. I didn't study RF, but my classmates in RF were all using Balanis for their RF and Antenna design courses, which clearly comes before the level of EM where most people are working (suffering?) through Jackson, or Balanis's 'Advanced Engineering Electromagnetics'.