The preposition 'into' allows for this flexibility in word order, but you're right because the sentence can rewritten in the more common form you're familiar with: In this chapter we compress the major issues we've discussed so far into summary form. I imagine the author chose this less common, but still legitimate, word order for stylistic reasons. The meaning doesn't change though.

Will you try this link? https://dictionary.cambridge.org/dictionary/english/compress?fallbackFrom=british-grammar Your answer is in the second entry.