Compensation for reviews is not common, but also not unheard-of. That in itself would not raise a red flag for me, and Elsevier is certainly a reputable entity in science publishing (despite their somewhat unfortunate role in the current struggle of academic publishers versus open access).
That you sometimes get invited to as an expert for fields that are not actually that closely related is also not extremely uncommon. The people that select reviewers for books are usually not experts in your field, so what appears to you as a significant difference in e.g., research approach or community may look like a mere technicality to them. You should decide for yourself whether you will be able to conduct a high-quality review despite being in a different field, and if not reject the review.
The only aspect of the request that I also find highly suspicious is that the request came from a personal email address. This alone would not be enough for me to outright discard the email as spam, but I would certainly not e.g., forward them my banking information before I don't get anything a bit more official than a mail from a GMail account that says that the person works for Elsevier.