Each unlocked scenario will be a standalone individual book (they'll basically look like magazines). So for each of the BOOK+X SCENARIO rewards, you'll get the book (rules, character templates, 5 basic scenarios) and then a separate "magazine" per Scenario based on how many you're getting per your pledge level.
For example: If you pledge at the $35 level for the BOOK+2 SCENARIOS, you will select two of the unlocked Scenarios at the end of the campaign. Say you select HATCH FEVER and TERROR AT TRINITY - then, when your reward is delivered, you will receive 3 physical books, the basic book and then two "magazines" each containing one of those Scenarios.
If you go for the $50 or $80 levels, in addition to the above you'll get the cards for each unlocked scenario you're getting, along with the basic card set. (There is some variation in how many cards are needed per scenario)
For example: If you backed at the $50 level and selected those same two Scenarios, you'd receive the above plus a deck of cards including all of the cards for the 5 basic scenarios and the two you've selected.