Just in case this bundle is bringing some of you your first taste of David Weber's Honor Harrington series, A Rising Thunder is the 13th book in the series. Sometimes, when Baen publishes these in hardcover they include a CD with all the previous works in the series (plus usually some other books as a bonus). They did this with Mission of Honor which was the 12th book in the series.
While I have been aware of the CDs for awhile, I have only recently learned that Baen has a fairly liberal license for the CD's such that someone is hosting their content on the net with Baen's tacit blessings. So, if you want to start at the beginning of that series you could go to the Mission of Honor CD at http://baencd.thefifthimperium.com/
and download all of the previous 12 books plus 5 anthologies and 4 other books in other branches of that universe. You can either download entire images of the CDs as ISO or ZIP files, or just download the books individually in the format you want and save some bandwidth (if not yours, his).
Have a great day!
Edit: That said, it wouldn't hurt to reward the munificence of our benefactors by going to baen.com and buying something that isn't on the CDs.