HereAmazon Link is the Amazon link to Lichens of North America, which is what I’ve been recommended. Like I said, it is much pricier, so I haven’t made the purchase myself. I’m not sure if a local library might have or be able to request for readers to check it out.
You should check out Lichens of North America. It's a key and a textbook of Lichens.
Lichens of North America https://www.amazon.com/dp/0300082495/ref=cm_sw_r_cp_apa_jgHKyb0B0AQ4R