Metal halide lighting would certainly do the trick but it can generate a lot of heat, especially beneath a canopy. You will want to seriously consider fans if you go with MH
lights. If you do, I would suggest two 150w MH
lights, and those only if you also have a CO2
I would suggest T-5 high output lights as an alternative. I believe Hiscock's book predates the introduction of T-5 lighting. T-5s have considerable light output per watt while remaining very cool and you can pack a lot of them in a small space. They would be an excellent solution for a 90G with a canopy. CurrentUSA makes a series of T-5 lights called the Nova and Nova Extreme series. They are now quite affordable and give you a lot of options as far as spectrum. Most of the large online retailers carry them.
Hope this helps