I Spy vs In Secret: Which Should You Read?

I Spy Natalie Sumner Lincoln · 1916 ★★★★☆ 3.5 221 pages · ≈ 4 h 06 m · Challenging

The allied forces, English and French, had been bent backward day by day, until it seemed as if Paris was fairly within the Germans' grasp. Bent indeed, but never broken, and with the turning of the tide the Allied line…

In Secret Robert W. Chambers · 1919 ★★★★☆ 3.9 246 pages · ≈ 4 h 33 m · Challenging

The case in question concerned a letter in a yellow envelope, which was dumped along with other incoming mail upon one of the many long tables where hundreds of women and scores of men sat opening and reading thousands…