Hey Olivia, Just now there are many great books about Maria Montessori, her own writings and interpretations of her methods by other authors. If you have a kindle or tablet with kindle app, you are in luck because many of these books cost very little in this format.
Personally, I find the methods used by Maria Montessori truly inspirational yet eminently practical. She learned about children not by reading scholarly articles, but by observing their behaviour. She was truly a wise and gifted woman.
ps, why not mention the name Montessori in the heading to your question, It could attract many more relevant responses.