Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A Required Reference

This is a standard, required reference for anyone working with fungi/lichens...the cost vs eg "The CRC Lichen Handbook" ca US$400 makes Ainsworth esp desirable; tho they compliment each other very nicely...the binding is durable (perhaps a bit loose), the cover boards are sturdy, the type face readable; altogether an affordable text and will be frequently used.