Because everyone is familiar with Frontinus and is eager for more information about aqueducts and Roman water-supply, allow me to recommend A. Trevor Hodge’s charming survey Roman Aqueducts and Water Supply. Hodge eschews incomprehensibility (in so far as possible) and has the virtue, which Ashby lacks, of a modern bibliography. He is, however, rather chatty which somewhat lowers the ‘tone’, e.g.:
Administrative techniques are his forte, and engineering is really of interest to him only in so far as head office had something to do with it. When I was a boy, our school library was full of improving works with titles such as The Romance of Engineering. That is a concept which, when you get right down to it, Frontinus would not have understood; but he would very likely have substituted for it something even more alien to our own attitudes—The Romance of the Filing Cabinet (18).
If you are absolutely desperate, though, to learn about Roman water supply from fontes to cloaca, Hodge is as good a place to start as any. Also of interest (though I have not, myself, seen them yet):