One of the first, and best, erotic manga I have had the pleasure of reading is Take On Me, by 竹村雪秀 / Takemura Sessyu, a manga which has run into two volumes and attained no small popularity. It is not hard to see why; his works possess an immaculate and detailed style, engaging story and characters, and cover a broad range of sexual interests.
His magnum opus is certainly the two volumes of “Take On Me”; this is really a most accomplished work, especially artistically, but it also possesses a good and quite amusing (if entirely sex-centric and quite contorted at times) story and, particularly in the second volume, covers just about every mainstream sexual interest going.
An English language version is also available as “Domin-8 Me!”; I have no idea what their reasons were for changing the name, nor have I seen this version, but it may be worth a look if you are after an English language edition.
If I were to venture some mild criticism, it would only be that his style is at times a little plain, and sometimes over-stylised, and his colour illustrations are not at the same standard as his monochrome work. The story also can also be strained at times, not that his would really be considered story centred works.
He has also produced some slightly strange original dojinshi (I am thinking particularly of the Post Girl one with Junichiro Koizumi); these are actually quite good – well worth checking out, I think.
“ナタリィに銃と花束を”, “Guns and Roses for Natalie”, is his previous compilation – he has certainly improved a great deal from this, although it only looks bad in comparison to his later works. Interesting to see how his style and art develop (and what happened to all the futanari?), but it can be a little painful to put them side by side with his later works.