His Modeling Tanks and Military Vehicles is a must have, although its a bit of a time piece considering the newer techniques you all now have like filters, dots etc. But yah gotta learn to boil water first, right?
I was particularily educated by his intro chapter about research, where he discussed how to learn about a subject through reductive thinking. His example IIRC, was that if you called Aberdeen and asked "what do you know about the Sherman tank?" they'd never call back, but if you asked "how were the engineers tools on the M4A1 secured", someone with that interest would give you all the info you ever needed. In other words take your time, use your own skills as much as possible and proceed in steps.
I (and excuse me here Mr. Paine its just my opinion) think his strength is armor. To be certain his a/c dios are great, but tend to be over detailed, in the sense that I think he was playing to Monograms tendency to sell models with all kinds of removable panels. Having all kinds of open stuff is ok, but if the same kit can't be built with all of those panels buttoned up tight and look clean, it's limiting. The ones that come to mind are the P-80, the F-86 and the very problematic P-61.
He ranks with the likes of Dave Frary and Malcolm Furlow.