it's hard to know exactly how to answer this because we don't know your level of expertise and what exactly you mean by "brain mapping," which is a wide-ranging field. but, assuming you're doing some kind of fMRI, i'd recommend the 3rd edition of Huettel et al's "Functional Magnetic Resonance Imaging" textbook, as well as Russell Poldrack's new "The New Mind Readers: What Neuroimaging Can and Cannot Reveal about Our Thoughts"