I've received an email from Lambert Academic Publishing (LAP Publishing), offering to publish my manuscript.
I heard that they are a scam, but is there any reason to refrain from publishing with them?
Note that my math book is published online as open source (with a free license) LaTeX (and PDF). I have almost no hope to publish it conventionally with a serious publisher (some publishers said my book didn't have enough readership, some declined because it is already available online.)
I won't lose the copyright because they do not require copyright transfer.
So my question: Enumerate all reason (or is there none?) not to publish with them.
Note that I am not a professional scientist and have no degree.