Hypacrosaurus is one of those dinosaurs that is still actively studied and new findings pop up now and again that are interesting thanks to all of that study. Earlier this year, for instance, Bailleul, Hall, and Horner released a paper on PloSONE.org that announces what they contend is the first evidence of secondary cartilage ever found in a fossil dinosaur, from a Hypacrosaurus. The trio took thin histological samples from the facial areas of hatchling Hypacrosaurs to determine whether or not secondary cartilage could be found in dinosaurs and have released figures in their paper which show where they found the cartilage and how that compares to a modern bird's cartilage placement. It is a very interesting find and quite intriguing when anything, even something this small is newly discovered.
The second paper I found that is interesting is the original 1913 paper by Brown describing and naming the genus and species of Hypacrosaurus. Barnum Brown's paper about a new trachodont dinosaur is not the most exciting paper ever, but papers that name new animals are always interesting and fun to read, as fun as scientific literature can be, keep in mind. The last paper, a 2008 paper by Cooper, Lee, Taper, and Horner, is more specifically about the growth rates of predators and prey, but it does discuss the growth rates of Hypacrosaurus in its overall study of the predator prey relationship. The Royal Society website hosts the paper freely, which is a great service to amateur readers, much like PloSONE, and so if you are interested in the entire paper on growth, you can actually read it all, not like some papers we share here.