It began with a pig that died
E.B. White kept animals on a saltwater FARM in Maine. In 1947 he published an essay called Death of a Pig about buying a pig to fatten and slaughter, the pig falling ill instead, and his own increasingly desperate attempts to save an animal he had been intending to kill. The pig died. He was troubled by the whole arrangement.
Charlotte's Web, published five years later, is that essay solved. A PIG is due to be killed, something intervenes, and this time it works. White said he simply wanted the pig to live, and that a SPIDER he had been watching in the BARN doorway gave him the means.
Charlotte is a real species and the biology is correct
White spent a year reading about spiders before finishing. CHARLOTTE is named Charlotte A. Cavatica after Araneus cavaticus, the barn orb weaver, which is a real spider that really does build in barn doorways. Her egg sac holds 514 eggs, which is a plausible number, and White's editor's queries about spider anatomy survive in the archives.
Everything she does is something the species does. The way she wraps prey, the way the WEB is rebuilt each night, the fact that she dies after producing the egg sac, and the way the spiderlings leave the following spring by ballooning on threads of silk — all accurate. Orb weavers really do eat the old web before spinning the new one, recycling the silk. The only invention is the writing. It means a child reading about a talking spider is absorbing genuine natural history without being told they are.
The words in the web are chosen carefully
TERRIFIC, RADIANT and HUMBLE are not random compliments. They arrive in that order as an escalating advertising campaign, because CHARLOTTE has worked out that the ZUCKERMAN family will not kill a pig other people find remarkable. TEMPLETON the RAT sources the words from scraps of newspaper and magazine, so the vocabulary is literally salvaged marketing copy.
HUMBLE is the one that matters. Charlotte explains that it means both not proud and close to the ground, which is true of WILBUR twice over, and it is the word that wins him the PRIZE at the COUNTY FAIR. A book that is partly about the power of describing something well is a useful thing to have in a classroom.
The ending is the reason it lasts
Charlotte dies. She dies alone at the fairground after the crowds have gone, having saved WILBUR, and White does not soften it or arrange a reprieve. His publisher and several early readers wanted him to change it. He refused, and the last chapter deals plainly with the fact that her children and grandchildren go on living in the BARN doorway while she does not.
This is why it turns up on so many reading lists. Along with FERN, the GOOSE, the SHEEP, the RUNT, the SPINNING and the LOYAL FRIENDSHIP at the centre of it, children get a book that treats death as ordinary and survivable rather than hidden. Our spiders page has more on the real animals White was watching.