...from Adobe fonts? (Fonts including those funny Greek mathematical signs / fonts).
Or from some other place?
You might want to first check with whatever program or plug-in you are using to cerate mathematical expressions and equations. They often have very specific requirements as to particular fonts that they are designed to work with.
Yes, indeed: I'm doing a schoolbook of fysics in Mac InDesign, and I'm getting the content in Word with Mathtype equations. I know Mathtype equations comes converted like pictures when placing the text in InDesign. One good 3rd party addition is to use MathTools (not Mathtype) which gives the possibility to bring the Word / Mathtype text and equations to InDesign as fonts.
In Mac the Mathtype is a bit problem, but at the moment a good choice would propably be Mathtools (maybe have to get them both when starting to do the actual book. Now I'm doing the layouts). I got Mathtype trial, and Word text converted through MathTools (don't have the MathTools yet, and they don't have the trial yet).