Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Admiring, Excited, Curious
Watson's huge man-crush on Holmes really comes through in the tone in all of the stories featured here. Watson frequently speaks of Holmes in glowing terms, and it's very clear that he admires the man. Holmes is usually characterized by positive adjectives like "genius" here. Watson is like the president of the Holmes fan club, and he's often as enthusiastic as a fanboy at Comic-Con:
Far from feeling guilty, I rejoiced and exulted in our dangers. With a glow of admiration I watched Holmes unrolling his case of instruments and choosing his tool with the calm, scientific accuracy of a surgeon who performs a delicate operation. (Milverton.92)
Watson uses very positive diction, or words, to describe Holmes here, as someone skilled and "calm" under pressure. Watson's tone is also very excited here. Crime-solving is a fun adventure for Watson and he often describes his job with words like "thrilling," and "exciting" (Milverton.92). Danger and close-calls and crimes are part of the excitement in these stories and, accordingly, Watson's tone is rarely upset or anxious or depressed. He is occasionally irritated, usually with Holmes, however. But even that irritation can't drown out his overall admiring and enthusiastic tone.
[I]t did not elicit that word of curt praise which I had hoped for and should have valued. On the contrary, his austere face was even more severe than usual as he commented upon the things that I had done [....]. (Solitary Cyclist.60)
Watson gets irritated with Holmes in the ensuing conversation and responds to his criticisms with "some heat" (Solitary Cyclist.62). But Watson never stops desiring praise from Holmes; and the fact that Holmes critiques are as upsetting as they are highlights how much Watson admires Holmes.
The last major tone worth mentioning is "curious." Watson is eternally curious and speculates constantly about cases, people's motives, and Holmes himself. Here's an example:
I gave a start of astonishment. Accustomed as I was to Holmes's curious faculties, this sudden intrusion into my most intimate thoughts was utterly inexplicably. (Dancing Men.3)
Fitting with the umbrella tones of excited and admiring, Watson's curiosity works with these tones to create fun, adventure stories that are filled at times with a kind of wonderment, or amazement.