The Project Gutenberg online library is a Wunderkammer of books in the public domain available in a number of different formats, some of which include images.
Some recent interesting discoveries:
The Planet Mars and Its Inhabitants, a psychic revelation, in which the author describes the various cities, canals, and moral principles of our red neighbor and explains that "Printed books are used, but mostly for the very young, as information is usually transmitted impressionally."
Electricity for Boys, in which we are given many hands-on experiments because, "A boy does not develop into a philosopher or a scientist through being told he must learn the principles of this teaching, or the fundamentals of that school of reasoning. He will unconsciously imbibe the spirit and the willingness if we but place before him the tools by which he may build even the simple machinery that displays the various electrical manifestations."
Of Natural and Supernatural Things : Also of the first Tincture, Root, and Spirit of Metals and Minerals, how the same are Conceived, Generated, Brought forth, Changed, and Augmented, in which we are taught that "the Magnet and true Iron perform almost a like benefit in Corporal Distempers, having almost one kind of Nature in and with them, as it is with it in the Celestial, spiritual, and Elementary Intellect, between the Body, Soul, and the Chaos, out of which the Soul and Spirit went, the Body at last was found out of the Composition."
Half-hours with the Telescope: Being a Popular Guide to the Use of the Telescope as a Means of Amusement and Instruction, in which we are warned that "The feeling experienced by those who look through a telescope for the first time,—especially if it is directed upon a planet or nebula—is commonly one of disappointment."
Searchlights on Health: Light on Dark Corners: A Complete Sexual Science and a Guide to Purity and Physical Manhood, Advice To Maiden, Wife, And Mother, Love, Courtship, And Marriage, explains that "Dissipated single men, professional libertines, and married men who are immoderate, often pay the penalty of their violations of the laws of nature, by losing their vital power."