Define 'Best'....
My 'Best' is not your 'Best'.
See where I am going? The only way to get the 'Best' is to cherry pick the results
for every single book, and edit THAT as you go.
And just to throw a spanner in the works, Amazon is one of the Worse sources because what is posted is a Free-for-all in the content (I suspect, much Author/Publisher supplied).
Your biggest enemy is INCONSISTENCY. Yep! It is rampant, even on a single site. For the same Author. For the Same Series. Even the same Book (revised by ???) .
Next is PUFF & FLUFFERY in the description, Ads about upcoming, About the Author... "Joe Friday, where are you when we need JUST THE FACTS ABOUT THE BOOK." I want a just a Synopsis . No Raves. Trim out 'Best selling Author'... (I've never see 'Worst ever Author' here
)
Next is Cover
Ha! We have possibilities of any cover ever used by that title... from many regions... from many editions.
How do I know. My first use of Calibre was to document my 980 Paperbacks purchased any time from the 1960's on
In addition to Not Found, No ISBN (were on those).. Books that are still 'In Print', had switched Covers, Switched Publishers, Been Revised (to be PC).
OK, that is my Rant.
Advice is still 'Cherry Pick',
but from a selected pool of sites adjusted for YOUR Libraries content . IT WILL DIFFER from Joe's, mine.
Start With
Preferences: Metadata Download (also reachable from the MDE at the bottom).
This is where you start, by choosing sources (User Plugins will add more, so plan on revisiting here)
The Cover Priority is where you set the weight given for returned found covers.
On the Left is the Global stuff (applies to any source)
Back to the Left. See the button 'Configure...'? That allows us to fine tune each source as to what we don't want (out of the global allowed on the right)
This varies PER SOURCE (plugin). The options for each Vary. You need to 'check out what each offers. I have my Favs for Series, for Tags. There is only one Rating source: ME (I discard others. Unfortunatly that does not block those IN the book at add to library time)
BTW The Amazon one allows Country (server), Edition. Good stuff
FWIW, those 980 paperbacks never got 100% on complete metadata (my way). It took me almost 2 YEARS of frequent work on the pile. I also had a Flatbed Scanner to capture covers that were not available (or those were poor quality), or those were not my editions cover.
Happy Cherry Picking