>>139411National Audubon Society Field Guides are a good start although they can be region specific and I in my opinion they leave a bit to be desired. For plant and herbs based on your area a few you might look at are as follows.
A Field Guide to Western Medicinal Plants and Herbs by Steven Foster
Edible Wild Plants: A North American Field Guide by Thomas Elias
Plants Of The Pacific Northwest Coast by Jim Pojar
Edible Wild Plants: Wild Foods From Dirt To Plate by John Kallas
Mushrooms Demystified by David Arora
And the Peterson Field Guides.
>>139405any good handbooks, reference books, etc. to carry with me
Not clear on what you mean by reference books for plant reference the above will work. If you are referring to camping and outdoor skills some starters I would recommend are
The Boy Scouts Handbook
The SAS survival Handbook
Wilderness Survival by Gregory J. Davenport
The Complete Wilderness Training Book by Hugh McManners
All of the above a good starting points for camping type situations. If you are leaning more towards the SHTF scenario stuff for beginners I would suggest
When All Hell Breaks Loose by Cody Lundin
How to Survive the End of the World as We Know It by James Wesley Rawles
The List
>>139357 are all good titles although some are not great for beginners hence others that I listed.
I would suggest getting the dirt time above almost anything as most people learn best by doing in my experience. The majority of your urban type stuff and advice can be found on /k/ I hope this helps.