App for audio books?
I think the easiest solution is for you to use a program that lets you join your MP3 files into a single file that will be treated as an audiobook file on your iPhone, so that your last played position is remembered when you resume play, and so that you can use chapter navigation within the file to move to different sections. This also simplifies finding your audiobook on your device, because instead of over a hundred different files associated with that audiobook title you only have a single file, or perhaps two files for parts 1 and 2. There are programs that will do this on both the Mac and on a Windows PC. If you are using Windows you can try either:
- MP3 to iPod/iPhone Audio Book Converter from http://www.freeipodsoftware.com/
- Chaper and Verse from Loden Software
Those two sites offer their software as donationware -- free to download and try, but with the suggestion that if you find it useful and you are able to, that you make a donation to help support their ongoing development and support of the software. For the Mac, you can try either:
- Audiobook Builder from Splasm Software and also available from the Mac App Store
- Audiobook Binder from bluezbox and also available from the Mac App Store
Audiobook Builder is a paid app ($4.99, I think) and Audiobook Binder is another donationware app. I've linked to the developers' web sites, since you can download trial versions of the software there (and also find other license options), whereas that's not possible if you use the Mac App Store link. I think Audiobook Builder has additional features and options, and it's the one I usually recommend. In either case of using the Windows or Mac software to produce single tracks, it's recommended that you keep the individual joined tracks under 13 hours in length. Basically, the old music file formats like MP3 were never designed for muli-hour playback, so the time counters in their tag fields may not behave correctly if the number of music sample elements in the file gets too big.
I also recommend that you listen to the recent FSCast podcasts (Episodes 73 and 74, from December 2012 and January 2013) that Jonathan Mosen gave explaining iTunes 11. You can find them at the Freedom Scientific Podcasts site.
Once you add the converted files to your iPhone as audiobooks, you'll be able to listen to them in your Music app, or in the third-party Bookmark app that Anonymouse mentioned. While it's possible to download and play MP3 files in Downcast, you'd still have to deal with the over 100 separate book files, so you would first want to use an MP3 joining program, anyway.
Hope this helps.
I'll just comment that yes, you need to create an account with Audible.com and purchase audiobooks from their web site in order to use their Audible Player app. But the nice features are the selections of books and the prices (if you join one of their subscription plans), plus the fact that you can re-download any of the books that you purchase from your account's library at any future time. What is especially convenient about the Audible Player app is that you can wirelessly download audiobooks that are in your Audible account library directly into the app, without having to go through iTunes at all.
The Bookmark app allows you to set multiple bookmarks and notes within a single audiobook, has a novel design of a "time ribbon slider" that lets you navigate easily throughout long audiobooks and/or podcasts, and if you listen to audiobooks before going to sleep, there's a neat function where you can set sleep timer to cut off play after a fixed number of minutes, but extend that time automatically, if you're still awake by simply rocking the iPhone to the side. The limitations of the Bookmark app come from the fact that it is using the Music app -- so you can't use it to play books with Audible DRM, or podcasts that you've downloaded into third-party podcasting apps, and you can't get as fast a top playback speed as some of those apps offer. It should work fine for your MP3 audiobooks once you've converted them.
I use both the Audible and the Bookmark app.
Voice dream reader will actually work. You zip the folder where the book is and put it in to voice dream reader. It will then let you keep your place. I'v reading some books this way and it just rocks.
Voice dream is hardly the most cost effective. I would recommend simply converting the books to m4b.