I'm going to have to order one of these. Am I right in thinking that this is part of the series that also includes BOOT HILL and ACE HIGH?
yes, you are correct.
This movie is the first of the trilogy.
Unlike, other so called "trilogies" of the genre, this actually has a bit of continuity to it. Not that you have to see the three films in any particular order, but it is clear that the two protagonists (Hill and Spencer) are the same characters throughout the series.
Unfortunatly this is not a very good series.
I haven't seen the first, but I will soon. I'll come back to give input.
The second installment is considered "the best" of the Cat Steven's trilogy.
However it suffers from major pacing problems, especially during the final 30 minutes.
Boot Hill, the third and final installment, is not only the worst of the series but one of the worst spaghetti westerns ever.
This morning,I finally managed to see that decent print of GOD FORGIVES I DON'T and its a definite improvement.

However any pacing problems in ACE HIGH are nothing compared to the overall slowness of Colizzi's first film.Its the much grittier and more violent western and the opening scenes and shoot out finale is the best i've seen from Colizzi.But almost everything else in between whether its Spencer manfully struggling with a casket on his back,extended card games or torture scenes,its all way too much too drawn out ,in some cases to ludicrous proportions.Also as much as i enjoyed Frank Wolff as the gabber mouthed San Antonio evens his ramblings well outstay their welcome in places.
Both myself and the missus feel that ACE HIGH is easily the better movie.It has a much greater scope all round and most tellingly the humour(Wallach pretty much makes this essential) and i'm sure that Enzo Barboni (director of the Trinity movies)would've seen the comedic potential of Hill and Spencer from this movie rather than its predecessor.
Having quibbled about the slightly boring feel of GOD FORGIVES I DON'T i still enjoyed it but would only really recommend it to Bud 'n' Terence fans because without them i wouldn't enjoy it nearly half as much.
My rating for GOD FORGIVES I DON'T 6 out of 10.
and for ACE HIGH 8 out of 10.
