A bit late response: if you make use of Calibre - to tag your books, load them onto your Paperwhite, and transfer over metadata - the KOReader browsing options become vastly superior to the Kindle stock options.
- Calibre loads books on the device under author folders (by default), so the KOReader filebrowser allows you to easily browse by author's last name.
- The 'Calibre metadata search' feature allows you to 'Browse tags'. If you preface the most useful tags with a character (e.g. #Fiction-Historical, #Science) and limit the number of these tags, you get them listed in the first few pages of your tag browsing. To browse by gender include tags like #Female.
- You can also 'Browse series' via metadata search.
I don't know of a built-in way to browse by title, but you can use the 'file search' feature to look for a period, and the result will be a list of all your book files in alphabetical order. If Calibre names the book files on the device with their title first, this produces a sorted list of titles. Although there is no ability to then jump to a particular letter, you can jump to a page of that list.