It was two boxes. Imperial Starfire had diagrams extra etc. Starfire had maps. Both came with countersheets.
§rd Revised was a nice booklet. SM2 was a PDF, print yourself and changed a lot economically, diplomatically (more complex and interresting NPR's), and CFN wise.
UTM was the first result of the redesign group for 3rd. The unified rules manual never made it, and all other 3rd products where taken off the market at the same time.
I leave it to others to unravel what went on... But it was a loss to the Starfire community that 3rd was stopped and the rifting. But too many partisans involved, and other issues, so enough of it, I don't want to open a can of worms.
4rth and later editions I would play if there was a decent spreadsheet allreaddy around. I don't care about 'build your own' and the whole tech tree affair lacks a diagram showing how what is where connected, so too much of a hssle for me personally. Thus I play still 3rd edition. It's closest to the various novels, and to the pile of products I have, and it has a good computer support program wich makes bookkeeping for larger universes possible.