Lenny suggested Terry Pratchett's Discworld series.
Add one point to that, the book Mort was very good.
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[Recommended for you are]

Charles Darwin:

>> On The Origin of Species
>> The Descendent of Man

Richard Dawkins:

>> The God Delusion
>> The Selfish Gene

Albert Einstein:

>> Relativity - The Special and General Theory

Stephen Hawking:

>> A Brief History of Time

Friedrich Nietzsche:

>> The Antichrist

Bertrand Russell:

>> Why I am Not a Christian

Carl Sagan:

>> Billions and Billions