[Orwell1984]

I reached out to Helion & Company about the titles below which look like multi-volume re-issues of previous titles. They confirmed that there is no new content in the titles, just being re-issued in a new format.

Air Battles over the Baltic 1941 Volume 1-4 by Mikhail Timin

Air Battles over Hungary 1944-45 Volume 1-4 by Dmitriy Khazanov

Lend-Lease and Soviet Aviation 1941–1945 Volume 1-4 by Vladimir Kotelnikov

So if you already have the older single volumes save your money!