The Book of the Tulip, A. Daniel Hall, Stokes, ND, preface says 1928, has a few photos of bybloomens. (RdV)

Garden Bulbs in Color, J. Horace McFarland, R. Marion Hatton and Daniel J. Foley, J. Horace McFarland Company, 1945 but there are many editions from 1938 on. Good for early 20th century varieties, lots of photos. (RdV)

The Genus Tulipa, A. D. Hall, The RHS, 1940. though dated this book is essentially the standard reference for taxonomy. (RdV)

Notes on Tulip Species, by the late W. R. Dykes, Ed by E. Katherine Dykes, Herbert Jenkins, ND (late 1920s he died in 1927) a rare large folio monograph on some species with personal notes by the godfather of modern Iris. (RdV)

Tulips (part of the Garden Flowers in Color Series) , Rev Joseph Jacobs, Stokes, (ND, but preface is 1912. very good small volumn for early 20th century varieties. (RdV)

Tulips Species and Hybrids for Gardeners, Richard Wilford, 2006, Timber Press, the most recent contribution but very limited on hybrids (RdV)