FYI, I don't own a Kindle, I Pad or any other fancy e-book reader. I just find these and save them as adobe pdfs on the hard drive of my macbook. All of them cam (as my Irish father-in-law would say) free, gratis and at no additional charge.
Here's a sampling of the more useful books I've found for Naval warfare in the late 19th and early 20th centuries. I know that similar treasure troves are out there for other periods (for instance the James' history of the Royal Navy 1793-1815 is available in its entirety).
Books available online
1. Brassey, T.
a. The Naval Annual (1886, 1887, 1888-9, 1890 & 1902 editions – I am still trying to track down the 1896 and 1898 editions – these are valuable troves complete with plans, armour and weapon details and squadron Orbats)
2. Cassard, W, G
a. Battleship Indiana and Her Part in the Spanish American War, 1898 (by her chaplain!)
3. Gibbs, F.T.
a. Illustrated Guide to the Royal Navy and Foreign Navies, 1896
4. Goodrich, C. F.
a. Report on the British Naval and Military Operations in Egypt, 1885 (prepared for the US Navy)
5. Jane, F.T.
a. The British Battlefleet, 1915
b. Heresies of Sea Power, 1906
c. The Imperial Japanese Navy, 1904
d. (Copies of Jane’s Fighting Ships are so far proving elusive)
6. Jones, H.W.
a. The Battle of Santiago On board the U. S. Battleship "Texas", 1913 (another chaplain at Santiago)
7. Lodge, H.C.
a. The War With Spain, 1899
8. Mahan, A.T
a. Lessons of the War With Spain, 1899
b. Naval Strategy, 1911
c. On Naval Warfare, 1918 (a selection of Mahan’s articles)
9. McClure, A.K.
a. The Naval Battle of Santiago, I am not sure of the publishing date but Cornell’s copy has a library stamp from 1903!
10. Reed, E.J.
a. Modern Ships of War, 1888 (with Simpson and Kelley)
b. Our Ironclad Ships, 1869
c. (Reed was a controversial former chief constructor for the Royal Navy)
11. Schley, W. S
a. The Battle of Santiago, 1898 (Schley was in charge of the US fleet for the first part of the action – this was his action report)
12. Stevens, G.W.
a. Naval Policy, 1896
13. US Office of Naval Intelligence
a. Some Information Concerning Some of the Principal Navies of the World, 1909
b. The Views of Admiral Cervera, 1898 (the view from the other side)
c. War With Spain, Operations of the US Navy on the Asiatic Station, 1900 (Dewey’s reports)
14. Wilson, H.W.
a. The Downfall of Spain (Naval History of the Spanish American War), 1900 (the best resource for this War)
b. Ironclads In Action, 1896 (classic resource covering 1855-95)
c. Japan’s Fight For Freedom, 1904 (covers early parts of the RJW, and yes that is the actual title)
d. I am still looking for Wilson’s “Battleships in Action” covering Russo-Japanese War and WWI