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you can't go wrong getting the tech readouts - the histories of each mech are pretty cool to read, especially the 3025 and 3050 ones
novel-wise, the best and easiest to read novels are the Robert Thurston/Jade Phoenix trilogy - yes it's kind of jumping ahead since they are clan books but technically these novels start around 3030 way before the invasion of the Inner Sphere so it's not far off the 3025 beginning of classic BT, and they are very well written and addictive books
http://www.epubbud.com/search.php?q=Robert+Thurston&Search=Search
next are the Robert Charrette books like 'Wolves on the Border' - also very well written, but i found there's so many characters i never really knew who was in what scene lol
http://www.epubbud.com/search.php?q=Robert%20N.%20Charrette
the most complete and chronological series was all of Michael Stackpole's books - not as strongly written as the above but still a very enjoyable read and a much more thorough history of the Inner Sphere
http://www.epubbud.com/search.php?q=stackpole&Search=Search
you can read the novels on your android phone with FBreader
https://play.google.com/store/apps/details?id=org.geometerplus.fbreader.plugin.pdf