Hi yakevigatad,
Open Scribus without a file opened, and edit the preferences to change the on screen preview to low resolution and then try to open your file, see attached. Then as utnik suggested, break the book down into smaller sections such as chapters or by pages. I regularly have done booklets that are 80-100 pages, just not image intensive as your description and have no problems. I am not real good with xml, but there might be a way to edit the file in a text editor to make smaller sections without having to open the file in Scribus, maybe someone else could chime in on this.
Cheers!
mnawij