If you want to increase your chances of getting back those books you lend to friends, maybe you could make this your bookplate (does anybody have bookplates anymore?):
"For him that stealeth, or borroweth and returneth not, this book from its owner, let it change into a serpent in his hand and rend him. Let him be struck with palsy, and all his members blasted. Let him languish in pain crying out for mercy, & let there be no surcease to his agony till he sing in dissolution. Let bookworms gnaw his entrails ... when at last he goeth to his final punishment, let the flames of Hell consume him forever."
quoted by Colin Reid in the UK Filmmakers Network bulletin.
ps: Maybe can also adapt this--"For him that pirateth this digital file..."
(If someone has borrowed your copy of 'Your Writing Coach,' odds are you're not getting it back--it's too good to return! Better pick up another copy at Amazon or your other favorite online or offline retailer.)