Main Lesson Journal (Hbk) Landscape – Spiral Bound Classic Hardback Main Lesson Book. These lesson books feature heavy 120 gsm chlorine-free paper which is well-suited for use with crayons or ink. The cover is 280 gsm (73 lb.) thick card stock with leather impression. Back cover is 2mm thick hard cardboard and does not bend easily making it suitable to take outdoors or use where a table may not be available. Perfect for projects.