How many drafts are normally required when writing a book?

There are already satisfactory solutions to this matter, but it is entirely subjective and relies partly on personal experience and methodology. I must mention that I do not engage in multiple drafts, so I would advise against following my approach.

In my initial attempt at writing a novel, I completed three drafts. Unfortunately, the final draft was only slightly better than the first, although I did notice some improvements. Notably, there was more dialogue and less exposition, which effectively taught me how to write. It took me over two years, working part-time, to complete this endeavor. However, it goes without saying that the result was still quite terrible.

A few years later, I took a couple of screenwriting courses and wrote a screenplay that surpassed my previous work by leaps and bounds. I only wrote a single draft, which received positive feedback from several individuals. However, they suggested rewriting it solely due to its technical complexity for screen adaptation, involving animatronics and special effects. Eventually, I submitted it to film producer Douglas Stanley, who provided intelligent comments and asked relevant questions. I added some exposition scenes, as suggested by him, but he expressed satisfaction with the overall script. Unfortunately, he struggled to garner serious interest from others without assembling a "package" with renowned names. Subsequently, I did not pursue further screenwriting.

Approximately ten years later, I wrote a novel titled Elvene, which Douglas Stanley acknowledged as having a cinematic feel and good translation potential. Elvene was composed intermittently, with Part 1 taking six months, Part 2 consuming an additional two years, and a twelve-month hiatus in between. The novel consists of roughly equal parts, totaling around 95,000 words. While I enlisted up to three editors, they did not request rewrites or alterations to the structure or pacing.

Since then, I have written two sequels, forming a generational trilogy with different protagonists, while the only constant character is an AI entity.

My writing process always begins with creating "sketches" in a notebook, which contain various what-if scenarios and backstory. I revisit these sketches when I face obstacles. Additionally, I maintain a separate file on my computer with alternative scenes or unused ideas. Generally, I am unsure of the story's conclusion until I reach it; however, I do need some key plot points to guide me.

Although I can endlessly edit, I do not engage in the practice of rewriting. This is because I know that my second draft would likely not surpass the initial one. Someone once said that leaving a written piece for a period of time and returning to it can help determine its quality, and that is precisely what I have found to be true.

I have only encountered one individual who has read all three of my novels, and they were unable to put them down. Hence, I know that my method works for at least one person. However, I must reiterate that you should not follow my approach as it is time-consuming. Instead, you should discover what works best for you.