There's a book that describes what Christians believe about the life of Jesus Christ, and is used by most Christian priests to illustrate and reinforce their homilies and lessons to their lay folk. The same book is widely read by many denominations of Christians as a source of insight into the religious intent of Jesus Christ, even if the conclusions they draw from it may vary.
There are also other books written by both lay authors and those with theological credentials that seek to describe what a "good" Christian should believe and do, though to be fair, none of them are universal across the Christian faith (*).
No such work exists for "secularists".
(*) though fair enough, even "The Bible" doesn't entirely meet that standard given disagreements between both the high level denominations (Orthodox, Catholic, Protestant) and the subdivisions within each.
Because the Bible is not a single book but a complex arrangement of at least 66 books (Roman Catholic Bibles include another seven books that Protestants do not recognize) written over many years by multiple authors, the question concerning versions can be complicated.
One major division is stems from Old Testament versions; Roman Catholic Bibles are all derived from the Septuagint version (3rd Century BC translation of original Hebrew scriptures into Koine Greek) of the Old Testament, whereas Protestant Bibles returned to the original Hebrew texts.
There are over 450 known versions of the Bible in English alone.
While there are estimates of several thousand distinct christian dennominations, the *major* categories are Catholic (50.1%), Protestant (36.7%), Orthodox, including Eastern and Oriental communions (11.9%), Other (1.30%).
I don't mean to nitpick, I grew up in one of the last "remote areas" of the planet and we were inundated with missionaries (when listed (now not) we had at least a hundred different types of christian mission here) that all had beliefs that only superficially appeared similar.
One wing of my larger extended family is fractured by a run of Christian brothers and sisters all raised catholic, all with military service, and all progressing to different barely compatible denominations and scarcely talking since.
> No such work exists for "secularists".
Secularists also have at least 66 books to draw on for morals, ethics, and common human values. It's debatable whether a book is even required to act with cooperation and respect with most others.
There are also other books written by both lay authors and those with theological credentials that seek to describe what a "good" Christian should believe and do, though to be fair, none of them are universal across the Christian faith (*).
No such work exists for "secularists".
(*) though fair enough, even "The Bible" doesn't entirely meet that standard given disagreements between both the high level denominations (Orthodox, Catholic, Protestant) and the subdivisions within each.