I must admit, when I bought both IB and HS, I was not very well educated in poetry; and inevitably, that threw me off both collections almost immediately.
Developing patience and a knowledge for literature, I returned to these poems. I'll put that down to watching a discussion between the poet himself and actress Mary Louise Parker at the NY Public Library (check it out, if you haven't, think it's available to download on the NYPL website).
I should say, if you are new to the man's art, try Infinity Blues first. This will help you familiarise with his writing style, and his (often absurd) imagery. If you have the patience to work your way through the first book, picking up Hello Sunshine should not present itself as a challenge, and in fact, you might be surprised by the much more mature writing.
Having said that, the poems in Hello Sunshine are still some of the most off-the-cuff free verse poems you may ever read, but taking them slowly and reading them over and over may do wonders.
In the NYPL discussion on poetry, the two quoted poet Mark Strand to have said something along the lines of, "You don't have to necessarily 'get' a poem straight away... you should let it wash over you." And never could a quote be more true of a collection of poetry.
The first poem that I heard/read from this collection was 'White Diamond'. At first, I dismissed it as simply a series of words slung together in a rhythmic pattern. Then I re-read it, listened to him read it at the NYPL discussion, and eventually, I got it. The lines "staring blankly into screens", "unaware of how pretty it is to be out walking in all these amazing places" and "we always loved each other this much, before the screens went on" all seem' to point towards it being about technology taking over, and our emotions being numbed by this 'unhappy voice' that seems to surround us now.
And what a message that was...
So on initial reading, this may seem 'half-hearted', and perhaps some of it is; but if you familiarise yourself with free verse poetry (perhaps read some E.E. Cummings), then eventually, the imagery might decode itself.
Re-read, re-read, re-assess. And perhaps the reward might be worth it.