I came across these three books (all by the same author) accidentally while Googling for something else. There were enough excerpts and even full chapters available at the web site (link below after video) to satisfy me that I wanted to read them all. All are available as printed books or as printable PDF downloads.
The one I enjoyed the most was "Start your own computer business". This is 162 pages, well written, with good humor and full of practical advice for the person starting out on a shoestring. I laughed as I read the first chapter, which examines an imaginary "first sale" that goes tragically wrong. I imagine every self employed person has had one or two situations like that where the only thing there is to be happy about is that you didn't lose more money than you did. Yes, I've been there and so has the author.
The book goes on from there to discuss all aspects of building and running a local computer repair service. I found that I agreed with every piece of advice offered. That's rare for me; I usually have more that a few bones to pick with self employment advice book. I suppose that's because so many of them set out to end up with you selling out your multi million dollar enterprise and retiring to an island - this is not about that at all. This is about starting a small computer repair shop, working it, and avoiding the easy mistakes that can cost you all your profits.
The other two books are "Computer Repair with Diagnostic Flowcharts - Troubleshooting PC Hardware Problems from Boot Failure to Poor Performance" (119 pages) and "The Laptop Repair Workbook - An Introduction to Troubleshooting and Repairing Laptop Computers" (191 pages)
The intended audience is people who have some small degree of computer experience - techie home user or beginning computer technicians. Therefore, it should be obvious that these three are not meant to be a set to be bought together, although the owner of a computer shop might buy the diagnostic books for their less experienced employees.
The Laptop book has much more advice of use to home users, but does also contain the diagnostic charts like the more general "Computer Repair" book. The diagnostic flow charts are followed by explanatory text for each decision point. Like the "Start your own computer business" book, these both contain practical advice that doesn't waste time with the obvious but does include tips from an experienced tech.