I just want to recommend https://www.amazon.com/Complete-Idiots-Saving-Starting-Guides/dp/1615641378
It's quite easy to understand, although there's far too few pictures.

These days i'm hoarding fruit and vegetables to save the seeds - even got frogskin melon-seeds which the seed companies doesnt seem to have - but i could have saved myself buying all those cucumbers if i had read this book first.
Next stop will be the grain-isles.