Mind and mindfulness themed specialist books.

"Share photos and ask lots of questions about the items you are buying and selling"

"If an ad or reply sounds too good to be true, it probably is"

"Use the 'Reply to ad' button for your safety and privacy"

"Don't reply to email addresses hidden in text and pictures"

"Trade in person, use PayPal 'paying for an item or service' to transfer money"

"Beware of fake Gumtree, eBay or escrow sites and invoices"