I'm looking for a decent textbook or books to self teach myself some advanced statistics. I may get the terminology wrong so applogies in advance

Possibly called Multivariate statistics?
When I have 3 or 4+ variables to undergo testing, that could be related in some way...
I have protein quantity vs dosage vs orientation vs spacial distribution vs time and looking for any patterns in that data, eg Normal distributions, spatial patterns etc... I'd be very interested in any recommendations in this regard as it's going to make up the backbone of my future thesis work in about a years time

Coefficent of bimodal distribution?
I worked this coefficent value out from a formula I found in a paper (which apparently is part of SAS), but I don't understand the underlying principals for the formula >0.555 being bimodal and whether or not there is a better way to verify that a distribution is bimodal or not , I looked but didn't see anything. So I guess what I'm asking for is a good reference for multimodal stats... and if the coefficent of bimodal distribution is reliable and whether the coefficent errors are generally Type I or Type II errors?

Thanks in advance,