The book tells you a story before you’ve read a word of it. On the cover is Charlie Brown, carrying a baseball bat and dejectedly dragging his mitt, above the title in emphatic, meme-ish font: “WINNING MAY NOT BE EVERYTHING, BUT LOSING ISN’T ANYTHING!” And on in the inside leaf, written in pen in looping cursive: “I love you.”

The pocket-sized book of Peanuts cartoons by Charles M Schulz, charming in clashing red and orange, is one of Wayne Gooderham’s favourites. “Everything about it works,” he says, leaning over the cafe table laden with his finds. “Charlie Brown on the cover, the title of the book, the sentiment inside – the fact that it’s been given away.”

As the curator of Dedicated To…, a blog bringing together poignant or intriguing inscriptions inside secondhand books, Gooderham can’t help but imagine the past lives implied on their inner leaves. Over 10 years, the project – born of his scouring secondhand bookshops for particular Saul Bellows and all Pnins, which he collects – has led to a publishing deal for Gooderham and inspired his fiction writing.

‘Everything about it works’ … Wayne Gooderham’s Charlie Brown book. Photograph: Wayne Gooderham

But though he delights in the “secret histories” of the books he finds, Gooderham does not these days write in those he gives himself. Why did he stop? “Because of this!” He nods at the stack of books between us: among them, a copy of Sartre’s autobiography, Words, with “I loathe my childhood” in huge type on the cover – and a correspondingly pointed address to “Mummy” inside.

The project has made him conscious of books’ long, migratory lives. “It’s made me more wary, I think, that they are likely to end up somewhere else … You see stuff and you think: ‘Oh my God – at the time, that meant a lot.’”

That someone can immerse themselves in following strangers’ paper trails, yet shy from leaving their own is testament to the highly personal – and often contradictory – policies by which people interact with books. It is not a straightforward division between those who like their books to look “lived in”; and those intent on keeping their collections pristine.

“It totally depends on the book and the copy, for me,” says Emily Hutchinson, a bookseller at The Second Shelf in Soho. “As a general rule, for paperbacks that have arrived to me in a rubbish condition, I just do whatever with them.

“If it’s something that is either particularly significant or particularly beautiful, I treat them with a bit more care,” she says. “But it’s a different kind of care if you’re making notes, carrying it around with you – loving it that way.” Hutchinson will write in the margins in pencil, and even dog-ear the pages; just the thought seems to scandalise Gooderham. “Never! Nevernevernever. I’ve got bookmarks.”

Among bibliophiles, the debate can be polarising and nuanced. For example: is it ever acceptable to write in a book? If yes: in pencil, pen or – heaven forbid – highlighter? Are all books fair game, or just some? And once they are so “defaced” – can you ever then give them away?

Hell is other people’s books … ‘Hetty’s’ gift to her mother

People who really put their books to work for them, such as academics, tend to devise elaborate systems. Hazel, an office manager, tweeted a photograph of her husband’s copy of Moby-Dick, thick with Post-it notes: “About 75% of his books are like this,” she complained. “He also did this to my Ivanhoe, without asking! … When you add 200 Post-its to a book, it does not retain its original dimensions.”

Gooderham follows a similar multi-step process before underlining – only books that he intends to keep, after a review of the Post-it page markers he left during reading. “It’s all very anal,” he says with a self-conscious laugh. But though he prefers to buy books secondhand, he finds other people’s underlining an unwelcome interruption to the reading experience: “When the line ends, I’ll stop as though it’s the end of the paragraph.”

From a bookseller’s point of view, it is black and white: a book with underlining has been defaced. Even just a line or two can cause the value to plummet by as much as 80%, says Christina Oakley Harrington, proprietor of Treadwell’s esoteric and occult bookshop in Bloomsbury. The exception is where the scribblings in the margins are by the author, or another notable figure. Then, “you’re kind of touching a piece of their inner intellectual and imaginative life”.

Oakley Harrington gives the example of Aleister Crowley’s poetry, written to his male lover at Cambridge: “He changed his lover’s name to ‘Christ’, ‘Jesus’ and ‘Lord’ so that it read as religious poetry and, in his copy, he crossed it out and wrote ‘Jerome’, ‘Jerome’, ‘Jerome’ – so secrets are sometimes revealed.”

Crowley changed his lover’s name to 'Christ' so it read as religious poetry. In his copy, he wrote ‘Jerome’

Some secondhand copies of Tanya Luhrmann’s anthropological study of contemporary London witch covens have the interviewees’ pseudonyms debunked in the margins – a case of the past reader contributing to the text, rather than detracting from it.

For some secondhand buyers, motivated more by sentiment than money, the traces of past readers are part of the appeal of what Virginia Woolf termed “wild books”. In his pursuit of a complete set of Picadors, author Nicholas Royle has amassed a collection of paraphernalia tucked inside their pages: business cards, boarding passes, photographs, cheques, currency, love letters. “I call these things ‘inclusions’, like flies or bits of bark caught in amber – because they’ve stopped time, in a way.”

How to woo a bookworm … Photograph: Wayne Gooderham

His favourite is a love letter “to somebody called Andrew, from somebody called Catherine”, written at 10.30pm on a Thursday, found in a hardback copy of The Duchess of York, by Lady Cynthia Asquith. “I’m quite nosy – I’m interested in stories within stories, and that’s literally that,” says Royle. “One story is about the Duchess of York and within it there’s this other story about the relationship between these two people. You’re thinking, ‘How did it end up here, how did it get given away?’”

Covering the walls of Skoob Books – in the bowels of the Brunswick Centre in Bloomsbury, London, where Gooderham finds most of his inscriptions – are finds from inside donations: postcards, photographs, foreign currency. (The most ever found was a US $1,000 note – though James, behind the counter, declines to go on the record about what happened to it.)

Some of these are powerfully evocative of past readers: it is impossible not to wonder about the person who carefully clipped a newspaper story headed “Forest trail ‘may lead to Bigfoot’”, now yellowed and curling on the wall above Skoob’s till. Sometimes, Royle says, he will buy a book he otherwise wouldn’t because of what he found inside it, which he is careful to keep on exactly the same page.

He himself treats books “quite carefully”, he says – not writing in them, never dog-earing. (“No! God no.”) When Royle comes across those he has written in secondhand shops, “I like to see that they’ve been well-read. I like to see the spine broken, and pages turned over, and names written in the front. But I would never do that to a book myself.”