This is possibly the most often quoted of all commentaries on the Book of Daniel.
It's scholarly to the point of being intimidating. Montgomery usually leaves quotations from Latin, Greek, Aramaic, Hebrew, German, and French untranslated. He uses abbreviations to cram 1000 pages of material into 500 pages.
Other commentaries from early in this century are getting hard to find (e.g., Driver, Boutflower, and C. H. H. Wright.) So you should buy this before it goes out of print.
I liked Montgomery's survey of the modern resurgence of literary criticism of Daniel. He sees Bertholdt's German commentary (1806) as the modern return to Porphyry's 3rd century criticisms of Daniel.
The book has wonderfully detailed histories of interpretations for controversial passages in Daniel. They are hard reading because of the abbreviations and untranslated quotations.