Massachusetts-based National Chicle Gum published their 192-card Batter-Up set in 1934 and 1936, as explored in more depth by Jason Schwartz on SABR's baseball card blog. Packages of their high series (#81-192) contained today's promotional bonus, a 20-booklet insert of "How To" pamphlets. At 3" x 4", they're larger than the actual cards, so came folded in quarters. Collectors folded it along the vertical spine to make a tiny book. Check the scan's vertical "guide," with back page to the left and title on the right.
National Chicle attributed this series to HOFer Rabbit Maranville, who played 23 seasons of energetic middle infield and chipped in 1 partial season as Cubs player-manager. While not a superior player, his firecracker personality and showmanship made Rabbit widely known. My second scan shows its interior pages and the meat of Rabbit's advice.
These 20 booklets (Old Cardboard gallery here) cover basic playing skills, but include interesting esoterica like "how to pitch the out-shoot," "in-shoot," and "drop." (In modern parlance, those are the slider, screwball, and sinker.) "How to Run Bases" covers the main points for any level of player: run everything out, move with the pitch, and watch your coaches.
Base running remains a major issue for teams, fans, and baseball writers. Today's era of more powerful lineups mean that managers worry less about scratching out single bases, yet team performance suffers if they neglect the station-to-station basics. (I will consider offers from MLB front offices hunting for Rabbit's helpful guide on base running. :-)
Value: Scarce premiums like this vary by seller. I picked up my #5 for $15 on eBay several years ago and now add to the set of 20 when I can find them for under $40.
Fakes / reprints: While it would be easy enough to photocopy National Chicle's "how to" set, limited collector demand also makes it a poor choice for fakery. Even so, be wary of a complete set of high-grade examples. Most booklets in the market today will be lower grade, since they were folded for packaging.
One legitimate reprint set does exist. Goudey acquired these instructional illustrations as part of National Chicle's bankruptcy sale in 1937 and added "how to" diagrams to the back of their 1938-39 R303 baseball premiums. Card sellers offered these to kids as a post-purchase promotion.
Can't blame the kid for gluing that back to something when R303 fronts look this good.
1930s cards feature a lot of leaping fielders and I'm here for it.