The first notable note is that a few writers are on both lists. Now I don't know whether this is evidence that you can't please readers all the time, but it appears some readers were quite disappointed in their initially favored writer's subsequent efforts. The reasons for declaring a book eligible for a list of worst reads were too varied to identify any particular trend. Some works were deemed boring, some difficult to read, some disappointing, and some poorly written (or edited) containing several spelling and grammar mistakes.
On the other hand, the reasons for declaring a book a best read generally tended to sound the same. They were described as well-told stories...excellent writing...great imagery, and relevant to Guyana and / or the Caribbean.
Last note...although I requested book suggestions, one person nominated Wordsworth McAndrew's poem "Ol' Higue," with a lengthy convincing explanation for its placement on any list of Guyanese best reads despite the fact that no "book" of McAndrew's work is available for us to read. Can't argue with that. Someone also suggested a poem by A. J. Seymour, but couldn't identify a particular book. So I listed his collected poems (2002), edited by Ian McDonald and J. de Weever.
Here they are in no particular order, your choices for best and worst Guyanese reads:
1. Collected Poems, A.J. Seymour.
2. Shape Shifter, Pauline Melville.
3. Poems of Resistance from British Guiana, Martin Carter.
4. Mercy Ward, Ian McDonald.
5. My Bones and My Flute, Edgar Mittelholzer.
6. Ol' Higue, Wordsworth McAndrew.
7. Palace of the Peacock, Wilson Harris.
8. Slave Song, David Dabydeen.
9. Ariadne & Other Stories, Ruel Johnson.
10. Wild Maami, Roopnandan Singh.
11. Suspended Sentences: Fictions of Atonement, Mark McWatt.
1. Fictions, Ruel Johnson.
2. Buxton Spice, Oonya Kempadoo.
3. Molly & The Muslim Stick, David Dabydeen.
4. The Ghost of Memory, Wilson Harris.
If you'd like to add a title and author to either list, please do so in the comments.