A book featuring extracts from Hitchhiker's Guide creator Douglas Adams' archive is to be published.

42, which is being edited by Kevin Jon Davies, is marketed as featuring "the wildly improbable ideas of Douglas Adams."

The book, which is due to be completed in 2022, has been crowdfunded via the Unbound platform, and in under 24 hours has gone from fully funded - which confirms Unbound will print the book - to becoming 150% funded, making it one of the platform's most popular titles.

The Unbound page describes the project as follows: "After his death in 2001, Douglas Adams's papers were loaned to his old Cambridge college, St John's - over 60 boxes full of notebooks, research, letters, scripts, jokes, speeches, to-do lists, hard drives and even poems.

"The book will reproduce in facsimile form extracts from the archive with explanatory text and footnotes to add context. Developed in close association with Adams's family and literary estate, 42 will be a full-colour, large-format hardback that follows his career from early collaborations with Graham Chapman to his work on Doctor Who, through the Hitchhiker years, Dirk Gently, his groundbreaking non-fiction book Last Chance to See and his later digital work. Alongside this are details of projects that never came to fruition like a proposed theme park ride and a TV series provisionally entitled The Secret Empire."

The book also features letters to Adams, contributed by his friends. They include his collaborator John Lloyd, HG2G star Simon Jones, producer Dirk Maggs, Stephen Fry, Sanjeev Bhaskar, Neil Gaiman and Infinite Monkey Cage presenters Prof Brian Cox and Robin Ince.

42 will be published on a yet-to-be-determined date in 2022, the year that Adams would have turned 70 years old.

Kevin Jon Davies, who is editing the book, first met Adams in 1978, and subsequently worked on a number of Hitchhiker-related projects with him, including The Making Of Hitchhiker, the 1993 documentary for BBC Video.

The comedy writer's family have endorsed the project, saying: "What Douglas loved more than a good idea was sharing a good idea, and whether it was the 1st or 100th time you had heard it, his obvious delight never diminished. It's a pleasure to share that delight with you in this book. We hope you enjoy it."

To publicise the Unbound page, extracts from his archive have been released to the press.

One of the notes reveals that he was having a crisis of confidence about his characters, writing "Arthur Dent is a burk. He does not interest me. Ford Prefect is a burk. He does not interest me. Zaphod Beeblebrox is a burk. He does not interest me. Marvin is a burk. He does not interest me. The Hitchhiker's Guide To The Galaxy is a burk. It does not interest me."

Elsewhere in the archive, a page titled "General Note To Myself", sees him telling himself: "Writing isn't so bad really when you get through the worry. Forget about the worry, just press on. Don't be embarrassed about the bad bits. Don't strain at them..."

The Unbound page is still open for new supporters, with pledges of different amounts resulting in different reward options. Options include a £15 eBook version, £30 for the hardback, or £50 for a collector's edition.