I really like
The Garden Primer by Barbara Damrosch.
It covers everything from tools, preparing the soil, to what you need to know about all kinds of flowers, vegetables, herbs, bushes, etc.
If you plan to go much beyond eatables, you might want to check out some of the books by William Aldrich and Don Williamson:
*Perennials for Illinois
*Gardening Month by Month in Illinois
*Tree & Shrub Gardening for Illinois
*Best Garden Plants for Illinois
*Container Gardening for The Midwest
*Annuals for Illinois
Each of these is a short paperback that costs about $15. Nice pictures and information about stuff that grows well around here.