You'll need more than one book, especially if you "... don't want to be taking any chances!"
Often one book will have a better description, photograph or drawing that another book will omit - the range helping you to identify something more positively (and conversely raising suspicions of there is any conflict). You'll also get a greater range of warnings of whether a species has been accepted as inedible, not worth eating or causes anaphylaxis in some.
If you're still unsure, collect a specimen - with permissions of course - and cross reference by any sources you can access - but nothing beats a good course with a reputable forager.
ATB
Ogri the trog