There are many, but the field is still wide open. Anyone with a particular domain experience should find a market.

There are lots of starting from scratch guides, and few focused guides.

for subject in ["Finance", "Contact Management", "Service Desk Automation", "Web Apps from scratch", "Web Apps on someone else's API", "Baseball Metrics"]: for language in ["R", "Go", "Python3", "Rust", "Lisp"]: print(f"Examples for {subject} in {language} would make a good book.")

edit: no idea how to smash indent-formatting into MD-for-HN

Prefix each line with two spaces, per the formatdoc page [0]

[0] https://news.ycombinator.com/formatdoc

  for subject in [
   "Finance",
   "Contact Management",
   "Service Desk Automation",
   "Web Apps from scratch",
   "Web Apps on someone else's API",
   "Baseball Metrics"
  ] : for language in [
   "R",
   "Go",
   "Python3",
   "Rust",
   "Lisp"
  ] : print(f"Examples for {subject} in {language} would make a good book.")

Thanks!