Unfortunately the images of his work in his online gallery are frustratingly small, given the relatively large scale of his work. You can find somewhat larger images on the blog portion of the site, which serves as the home page.
His site gives no information on medium or size of the works. At first I thought he might be working at small scale in gouache, given his use of areas of relatively flat color. It was only through the website of a gallery in which he is represented, McGowan Fine Art in Concord , NH, that I found he is working in oil, commonly at sizes of 24×48′ (60x121cm) or 31×60″ (79x152cm), though he does work in smaller sizes as well.
There is also little biographical information on Bonner’s own site, I found from an article in the Concord Monitor (pop-up ad warning) that he was born in England and has been living in New England, specifically Massachusetts, since the 1980’s. There is also an article in Yankee Magazine (pop-over ad).
In addition to images of work in various stages, there is a series of short videos on his site that show a bit of his working process.
Bonner’s paintings frequently are of townscapes or buildings in landscapes, in which the architectural forms, as well as the forms of their shadows and negative shape sky elements, are arranged in strongly geometric compositions.