This is the first CD box set I ever owned, and now after 10 years of ware and tear on the CDs, I'm buying it again. I can't say enough of how LZ shaped my childhood and teenage years and eventually got me playing electric bass in a few bands. We used to hash out "The Ocean" for about 10 minutes... Great CD collection.
My only complaint are the missing songs, which Box Set 2 provides (and gives you most everything LZ ever recorded). I was somewhat aghast when "Lemon Song", "That's the Way", "Good Times, Bad Times", "Down by the Seaside" and "Bring it on Home" didn't make the cut. But then again, the second box set includes all the missing tracks from this set, so I suggest throwing in the extra $20 for the second set. These two box sets include (I believe) a bit more than the 10 albums that LZ released, plus you get the nice book liners and have all the songs on 6 CDs, not 10.
If you are wondering where to start with your LZ collection, I recommend Led Zeppelin II (my favorite rock album of all time), and then this box set. You can't go wrong.