This poem is a classic example of someone being taken by surprise by beauty and just staring at it, wide-eyed and open-mouthed. On the other hand, the neatness and precision of the sonnet form might seem at odds with the speaker's spontaneous bursts of joy. We don't know too many people who speak in Petrarchan sonnets when they're happy. Also, the speaker spends a significant portion of the poem talking about how great the scenery is rather than describing it. The second half of the poem contains more description than the first.
Wordsworth was attracted to the scene by the juxtaposition (or contradiction) of a chaotic metropolis that seemed to be resting or "asleep."
Despite the absence of most people at such an early hour, Wordsworth "peoples" the city with inanimate things like the light, the river, and the houses.