Your printer should be good enough to do exactly what you need. If you are usng the printer only to prepare your book and print personal correspondence, an inexpensive inkjet printer will be fine.
If you want to prnt your own letterhead and brochures, you should consider a good 1200 dpi laser printer. You can easily find such a printer for under $500.
When considering the speed of a printer, remember that the speed quoted for
a laser printer is the speed at which it prints copies of a single page. That
is, a twelve page per minute printer will print twelve pages per minute when printing
twelve copies of page 1. However, when the printer is printing pages 1 through 6,
the printing speed depends on the complexity of the pages as well as the speed
of the printer. It may take one minute to print a single page for the first
time, but only one minute for the next twelve copies.