TL;DR: It’s a typographical error: for “ideas” read “ideals”!
“Ideals!” said my uncle; “certainly Ideals. Of course one must have ideals, else life would be bare materialism. Bare fact alone, naked necessity, is impossible barren rock for a soul to root upon. Life, indeed, is an unfurnished house, an empty glass in a thirsty land good and necessary for foundation, but insufficient for any satisfaction unless we have ideals. Or, again, ideals are the flesh upon the skeleton of reality, and it cannot live without them.
“It always appears to me,” said my uncle, "that the comparison of ideals to furniture is particularly appropriate. They are the draperies of the mind, and they hide the nakedness of truth. Your fireplace is ugly, your mere necessary shelves and seats but planks and crudity, all your surroundings so much office furniture, until the skilful hand and the draperies come in. Then a few cunning loopings and foldings, and behold softness and delicacy, crudity gone, and life well worth the living. So that you cannot value ideals too highly.
“Yet at the same time—” My uncle became meditative.
“I would not have a man the slave of his ideals. Hangings make the room comfortable, but, after all, hangings are hangings. Perhaps, now and then of course, I would not suggest continual inconstancy a slight change, a little rearrangement, even a partial replacement, might brighten up the dear old dwelling-place. An ideal may be clung to too fondly. When the moth gets into it, or the dust did not Carlyle warn us against this, lest they ‘accumulate and at last produce suffocation’? I am exactly at one with him there.
“And that, as any Cabinet Minister explains every time he opens a public library, is why we have literature. Good books are the warehouses of ideals. Does it strike you your furniture is sombre, a bit Calvinistic and severe try a statuette by Pope, or a classical piece out of Heine. Too much white and gold for every-day purposes then the Reverend Laurence Sterne will oblige. Urban tone may be corrected by Hardy, and Lowell will give you urbanity. And, however well you match and balance them, remember there is a time for ideals, and a time when they are better out of the way.
H. G. Wells (1895). ‘The Use of Ideals’. In Select Conversations with an Uncle (Now Extinct) and Two Other Reminiscences, pp. 18–19. London: John Lane.
This reference was spotted by Eleanor Fitzsimons on Twitter. I’ve quoted so much of the context to demonstrate that the context is satirical—when the narrator’s uncle says that “good books are the warehouses of ideals” he means that you can leave the ideals in the books and not have to think about them, until the time comes when it might be expedient or convenient to get them out.
This is a terrible quotation to use when you are intending to commemorate a writer: it says that the writer’s ideals can safely be ignored and forgotten, in the warehouse of his books, until the day when you might take them out and use them for background decoration, like a wall-hanging. But perhaps the choice is in keeping with the four-legged tripods.
Who turned “ideals” into “ideas”? The earliest instance I was able to find is from 1999:
Good books are the warehouses of ideas. — H. G. Wells (1866–1946)
Ben Jacobs and Helena Hjalmarsson (1999). The Quotable Book Lover, p. 4. New York: Lyons Press.