Yes, it was as good as the first series. First, there were characters we cared about - Leafpaw, Squirrelpaw, Brambleclaw, Tawnypelt, Crowpaw, Cinderpelt, Firestar, Graystripe, Sandstorm, Ravenpaw, etc. And an adventure. And, of course, Erin Hunter's simple yet descriptive writing style. And who could forget prophetic dreams? Ah, yes. These reasons are what made the original Warriors series good.
I have now realized just how much the first series depended on the tension of expecting a battle to happen anywhere, at any time. This suspense is a large part of what made me a Warriors fan. Midnight, while written well and with characters we care about, lacks this suspense. This is actually strange, since the plot is moving faster in Midnight than in Into the Wild. There was suspense and tension near the end, though, which was definitely something good.
I also realized just how much the original series depended on subplots. In Midnight, there are virtually no subplots. At least, none that I remember. The subplots in the original series were interesting, and a reason they were so suspenseful. I guess this is a factor contributing to the lack of suspense in Midnight.
When I say lack of suspense, I do not mean lack of interest. I have read worse books before. Midnight is an interesting book, but with a lack of battles, it can be viewed as boring.
There was one way in which Midnight surpassed the original series, however. Characterization. This is a very important thing in a story. In Warriors, the main characters had some sort of personality, and sometimes it was strong, but most of the time, the cats weren't really that different from one another. In Midnight, each cat has their distinct personality, and it is communicated in a much better way to the original series.
Not to compare it further to Warriors, Midnight is a pretty good book. Its lack of action in the middle and beginning could make a boring read, but the ending was superb. The writing was smooth and descriptive. The characterization was above average, if not great.
Midnight is a book worthy of bookshelves and libraries everywhere.