Both the books and training sites hosted here have been tested successfully on Chrome, Firefox, Internet Explorer, Opera, and Safari. Any reasonably-recent version of these web browsers should suffice.
However, as of early 2016, the new Edge browser on Windows 10 is not recommended for these sites, until a known defect in this browser is repaired. Namely, Edge's URL display popup, issued whenever a mouse (or stylus) hovers above a link, can overlay links in a page's lower-left corner, rendering them difficult to select, if not fully inoperative. Even when no hover is intended, it's nearly impossible to activate any lower-left links—the disabling URL popup appears immediately when the mouse cursor reaches the link, leaving no time for a click.
In the sites hosted here and others, this impacts both a bottom-of-page navigation toolbar, as well as any other link that happens to wind up at the bottom left of the page.
When hovering over any of the leftmost links in these sites' bottom-of-page toolbars, or simply trying to select them at all, Edge's URL popup may cover multiple leftmost links. For example, below are screenshots of the book site's main page before and after the mouse cursor is moved to the toolbar's left side; the URL popup hides multiple toolbar links, and disables them in the process:
More generally, Edge's popup can overlay and disable any hyperlink that happens to wind up at the lower left corner of the page, due to a scroll or general text layout. For instance, below is the scene for such a link before and after the mouse cursor reaches it; the URL popup covers and deactivates the subject link, as well as any other links to its immediate right:
All the other browsers listed above avoid covering such links by displaying the URL popup more intelligently—on the left or right of the screen, just below lower-left links, or in a separate status bar. In Edge, users must either avoid a hover on links at the lower left corner of the page (e.g., by using touch if available), or perform a haphazard negotiation with the obscuring URL popup, clicking just below it, or clicking while moving the cursor in hopes of activating the covered link.
For more background on this bug, see the pertinent but unfortunately unanswered Microsoft support threads here and here. I also filed a report on the Connect site, though its visibility is unclear, and there seems no other venue for bug reports from normal customers.
In its defense, Windows 10 was released just 6 months ago as this is being written, and Edge may still be in a quasi-beta state. Given the vehemence with which Microsoft is trying to impose Edge on Windows 10 users, though, they should at least fix simple behavior issues like this which other browsers solved long ago.
There may be additional reasons to give Edge a wait-and-see, but they are beyond this note's scope. Its initial, default "choices" of search provider, for example, may to some seem either ploy to keep novice users in the Microsoft fold, or unnecessarily dark humor...