I used to check on the Packt page where they gave a book away for free daily a few years ago.
Out of all of the books most of them were trash. There was a couple of really good ones in there. But all-over my clear impression from the books was that Packt has basically no lower bar whatsoever on quality.
I picked up all the Rust books when I decided to learn Rust a few months back. Fortunately, two were from the library (the Rust book and the Apress one), while the other I already had thanks to a Humble Bundle deal (the O'Reilly one). The Rust Programming Book is excellent (and also available freely online/via rustup docs --book, but I like to read on paper when I can). The O'Reilly one is a little out of date, but unsurprisingly comprehensive and answers some questions that were of interest to me (like that a match expression turns into a jump table automatically if the data an be appropriately indexed, e.g., if you're matching on a u8) and covers macros which the book does not. The Apress book, on the other hand, is a hot mess and often actively wrong (and important things like the distinction between String, str, OsString and OsStr are simply ignored). If I wasn't just blindly requesting stuff via my library's online catalog, I would have skipped it because I've never seen a good Apress book.
(edited to say Apress and not Packt. I'd forgotten which crappy publisher I was dealing with.)
Out of all of the books most of them were trash. There was a couple of really good ones in there. But all-over my clear impression from the books was that Packt has basically no lower bar whatsoever on quality.