Here's my favorite Ultra Kaiju reference book series
http://www.amazon.co.jp/決定版-全ウルトラ怪獣完全超百科-ウルトラQ%7Eウルトラマンパワード編-テレビマガジンデラックス-164/dp/4063045668/ref=sr_1_2?s=books&ie=UTF8&qid=1363699422&sr=1-2
http://www.amazon.co.jp/決定版-全ウルトラ怪獣完全超百科-ウルトラマンティガ%7Eウルトラマンマックス編-テレビマガシンデラックス-講談社/dp/4063045684/ref=sr_1_2?s=books&ie=UTF8&qid=1363699579&sr=1-2
http://www.amazon.co.jp/決定版-全ウルトラ怪獣完全超百科-ウルトラマンメビウス%7Eウルトラマンゼロ編-テレビマガジンデラックス-講談社/dp/4063048128/ref=sr_1_3?s=books&ie=UTF8&qid=1363699422&sr=1-3
They're the same series as the Godzilla book mentioned above. All full color. The first book covers Q to Powered, the 2nd Tiga to Max, 3rd is Mebius to Ultraman Zero & Mirrorman, Fireman, Jumborg ace. All of them are still in print. HLJ sells them as Ultra Monsters Complete if you search there.
Anybody know a good one for Rider & Sentai monsters?