While not having published a Strategy Guide (as opposed to Orions, the previous “big hit” on both iOS and the preceeding Windows Mobile), I've often mentioned I consider the quite new iOS port of “Spectromancer” (AppStore links: small-screen devices; iPad HD) the best card game on iOS. Opinions may differ, of course – I just prefer the way Spectromancer (and the very closely related Orions) is played to that of Magic (the Gathering) 2013 does.