Typically in the past, the "Historic Collection" sets haven't really had any subsets - just a 144 card set split between 72 cards for OB players and 72 cards for active players. This year's set is a little different. BBM decided to highlight particular years - either debut year, draft year or year of birth for players. Each highlighted year is its own subset. There are six cards for players who debuted in 1958, 15 cards for players born in 1947, 12 cards for players drafted in 1968, nine cards for those born in 1955, nine for ones born in 1965, six for players born in 1967, 12 for those drafted in 1989, 12 for those born in 1973, 24 for those born in 1980, 24 for those drafted in 2005 and (finally) 15 for those born in 1988. Despite these subsets, the set still follows the established tradition of there being 72 cards for OB players and 72 cards for active players (and the 72 cards for the active players breaks down to 6 cards per team as usual also).
A quick aside here - the NBP draft is held in the fall every year (or at least it has lately, I don't know if it has for its entire history). Since the draft is for players entering pro ball the following season, it's always labelled with that year, not the actual calendar year it has occurred in. So for example, the draft that just took place four months ago in 2011 was the 2012 draft. For the purposes of this set, however, BBM is treating the drafts by their calendar year, so the 1968, 1989 and 2005 "Draft Pick" subsets are for what are commonly referred to as the 1969, 1990 and 2006 drafts.
It's kind of an odd set. It includes a lot of big names for OB players (Koji Yamamoto, Hiromitsu Kadota, Hisashi Yamada, Atsuya Furuta, Kazuhiro Kiyohara, Yukio Tanaka, Yutaka Fukumoto, Keishi Suzuki, Tsuyoshi Shinjo, Kazuhiro Sasaki, Masumi Kuwata) and a lot of the younger NBP stars and prospects (both Yuki Saitohs, Masahiro Tanaka, Kenta Maeda, Hirokazu Sawamura) as well as some of the more established stars (Shuichi Murata, Michihiro Ogasawara, Tsuyoshi Wada), but because of the years being featured there's naturally going to be stars left out of the set (no Sadaharu Oh or Yu Darvish for example). What is odd is that like the Legend Of The Tokyo Big Six set, there's no card for Shigeo Nagashima, despite the fact that he debuted in 1958. I was also kind of surprised to see that despite the fact that the "Matsuzaka Generation" was one of the highlighted birth years, Daisuke Matsuzaka was not included in the set either (I don't think any of the Japanese players who played in MLB in 2011 were included in the set - Ichiro was born in 1973 so he's another notable exclusion).
I have to say that I find the cards a little ugly this year. The design seems to crowd the photos a lot and makes them look a tad claustrophobic. You can take a look at all of them at Jambalaya and see for yourself. Here's a couple sample cards: