This was a long time coming.
2.5+ years in the making, still unfinished, but it had to go out!
I started my book Deployment from Scratch with a validation and working 5 months full time before going part-time so I have something to eat ;). Many months later, I am now again working more on the book than for clients and doubling down on finishing it.
I was telling myself there is no point in selling an unpolished version of the product but got feedback from an early mailing list poll I did, and enough people showed interest in getting a beta product sooner.
Still, I was waiting for a more solid version and at least 500 people on the mailing list.
Starting last month, I started to sell to a mailing list of 600+, made 20 sales over the first 24 hours, and with two more updates to the mailing list, sold 80 copies in the first month which are slightly over $2000 before Gumroad fees.
This wouldn't be possible without the mailing list (really, make one) and my blog that is basically my only place to advertise it.
I am actively helping people that reach out, which led to the first super positive testimonial (which I didn't even ask for). I also collected the first four 5-star ratings on Gumroad, which probably feels even better than money.