Which book took longest to write?

We will discuss about 5 books which took longest to write

It took 20 years by the writer Michael Crinchton to complete the novel Sphere.

He took 12 years to complete its sequel that is is named as โ€œLords of the Ringโ€.

Alistair MaxLeod took 13 years to complete this book.

It took 10 years to complete this book.

It took approx 8 years to complete this book.

Read more about these books here