This pamphlet was published by the Daughters of the Utah Pioneers in 1990. The stories it contains deal mostly with the 1847 Mormon migration, but it talks about the handcart companies. the most impressive thing about this pamphlet is the bibliography, and I have two books on hold at the library as a result.
It does have a quote describing the Platte River which was very interesting. "[It was] too thick to drink, to thin to plow, hard to cross because of quicksand, impossible to navigate, too yellow to wash in, and too pale to paint with."
It includes general descriptions of sites and events along the trial. This would be a good travel companion, but it doesn't include directions like the pamphlet published by the Church.
It has some sketches of different sites, but the are mediocre at best.