Historical Romance books were both the heroine and hero are servants or working class/commoners etc. (NOT upper-class or aristocracy/titled/nobles or wealthy/rich main characters.)

1.
I Will Steal You The Stars: Scandalous Daughters of Duke Street Book 2
I Will Steal You The Stars: Scandalous Daughters of Duke Street Book 2 4.45 avg rating — 76 ratings
2.
Listen to the Moon (Lively St. Lemeston, #3)
Listen to the Moon (Lively St. Lemeston, #3) really liked it 4.00 avg rating — 852 ratings
2.
The Tinner's Daughter (Cornish Sagas, #2)
The Tinner's Daughter (Cornish Sagas, #2) 3.52 avg rating — 42 ratings
4.
An Unseen Attraction (Sins of the Cities, #1)
An Unseen Attraction (Sins of the Cities, #1) 3.90 avg rating — 5,051 ratings
4.
The Miller's Daughter
The Miller's Daughter 4.13 avg rating — 295 ratings
4.
How Frances Wainwright Learned to Love (Wainwright Sisters #2)
How Frances Wainwright Learned to Love (Wainwright Sisters #2) 4.41 avg rating — 54 ratings
7.
Helen's House
Helen's House 4.32 avg rating — 47 ratings
7.
The Rowan Tree
The Rowan Tree 3.75 avg rating — 53 ratings
9.
A Substitute Wife for the Prizefighter (Victorian Prizefighters, #2)
A Substitute Wife for the Prizefighter (Victorian Prizefighters, #2) 4.20 avg rating — 5,302 ratings
9.
The Shoemaker's Daughter (Cordwainers, #1)
The Shoemaker's Daughter (Cordwainers, #1) 4.25 avg rating — 351 ratings