As an earlier review failed to note, this is the translation of Sir Richard Francis Burton (1821-90). A noted Victorian literary figure, Burton produced a number of translations for middle eastern works with a very specific sense of them AS literature. This means a fine sense of freedom (i.e. the opposite of a 'literal' or scolarly tradition) among other things, as well as various hesitations in what could and could not be published at the time. At his best, Burton ignored these conventions rather shamelessly; this counts for a great deal of the fun in reading the book or any of his other works.
Customers complaining about the quality of the translation, the "thrift edition" format favored by Dover Books - really a wonderful institution precisely for making such quality texts available at such low cost - or the lack of illustrations shouldn't blame research so much as simply read the title of the edition offered here. Readers (or perhaps 'customers' works better) seeking a nicer edition of the Burton text in particular should look towards The Kama Sutra of Vatsyayana (Modern Library Classics). Otherwise, there is the Illustrated Kama Sutra of the Burton text as well as scholarly, if still friendly editions like the Kamasutra (Oxford World's Classics). As an insightful customer noted in an earlier comment, the original text was not illustrated; the introduction to Oxford World Classic edition discusses this at length. But for $3.50, this makes for a wonderful starting point nevertheless.