This book was written back when the only game in town Pascal-wise was Microsoft Pascal, which (astoundingly for a Microsoft product) was mostly standards icon pliant and thus entirely unsuitable for business applications. Don Etling's libraries change this, and make it only mostly unsuitable.
The code is pretty much bug-free, that isn't the problem. The problem is that to use them, you have to think like Don Etling. Do you want command-line parameters? They have to be specified in NAME=VALUE format. If there aren't enough given, it pulls them from a file like a demented INI file precursor. Do you want to read a file? Better hope it's on the command line or you'll have a lot of hoops to jump through. Want to write on the screen? If it's not in the format of a menu or pseudo-dialog box, too bad.
I bought this book from a used book store hoping to find useful Pascal tips and tricks. Instead, I got a journey into the mind of a man with nonregard for UI or API design. If that's what you want, great. If you want an actual library for DOS Pascal, look elsewhere.