The books you mention and diglloyd don't really overlap much at all. LLoyd's focus is on TAKING sharp photos - eg focus shift, characteristics of specific lenses, focus system inaccuracies, shutter induced vibration, etc.
He has a systematic approach, is thorough and his conclusions are well explained.
As with everything, whether it is worth paying for is totally dependent on a persons financial situation. The content, however, is worth the cost if you have the disposable means to pay for it..
If nothing else it is very interesting seeing his comparative tests (photographic) of the resolving power of m43 (E-M5) and other systems such as 5DIII and D800
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Ian
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