library(tidyverse)
library(magrittr)
library(stringr)
library(readxl)

directory <- "bunch/of/excel/files"

# Get an overview of all the Excel files and their sheets
sheets <-
  data_frame(file = list.files(directory, full.names = TRUE),
             sheet = map(file, possibly(excel_sheets, otherwise = NA))) %>%
  unnest(sheet) %T>%
  View(title = "Overview")

# Read in the first 20 rows of every sheet and display in Data Viewer
sheets %>%
  drop_na() %>%
  mutate(df = map2(file, sheet, read_excel, n_max = 20)) %$%
  walk2(df, str_c("[", file, "]", sheet), View)