You can't put a guy on the cover of a technical instruction book without inciting feminists who think your're being prejudicial by assuming that the book is therefore at too high a technical level and women shouldn't be able to read or understand it.
On the other hand...
If you put a pretty girl on the cover, you 1) run the risk of annoying femists by running a sex-appeal campaign to get guys to buy the book, and 2) imply that only girls need to read the book as guys don't *need* to read books to learn computer stuff.
Better still to have a technical book cover with 1) no people (why O'Reilly decided on Head First to get away from the animals, I'll never know) or 2) multiple people of mixes sexes/colors/etc, to imply that software development is really a team thing.
On the other hand...
If you put a pretty girl on the cover, you 1) run the risk of annoying femists by running a sex-appeal campaign to get guys to buy the book, and 2) imply that only girls need to read the book as guys don't *need* to read books to learn computer stuff.
Better still to have a technical book cover with 1) no people (why O'Reilly decided on Head First to get away from the animals, I'll never know) or 2) multiple people of mixes sexes/colors/etc, to imply that software development is really a team thing.