High Frequency wireless (millimeter wave) can deliver speeds well into the gigabits. At millimeter wavelengths you can aggregate hundreds of MHz of spectrum compared to the 20 MHz typical of today's wireless networks. High frequency antennas are very small, so it's practical to put 50 of them on a chip for massive MIMO.
Rappaport, Heath and colleagues are world leaders in research in millimeter wave high frequencies and MIMO. Rappaport's NYU Wireless Center has been sending teams out to get empirical data on frequencies like 28 GHz. They are testing in two of the toughest locations for a wireless network: Manhattan and Downtown Brooklyn. Heath at the University of Texas built one of the first MU MIMO testbeds.
With literally $billions going into 5G wireless research you need the latest information and best sources.
Many of the claims in traditional wireless textbooks are not proving out in empirical testing. This book is current & well-informed and likely to be the standard for years if the authors' issue regular updates. It's a technical book and not easy reading for non-engineers but the style is clear and the explanations well written.
For the record, I'm a technology writer who has interviewed two of the authors on several occasions. Rappaport was part of a webinar I did for the Marconi Society.