I am on Mac OS High Sierra 10.13.6 and R version 3.6.0 (2019-04-26).

Hi, Thanks for the reply. I am on High Sierra OS 10.13.6 and R version 3.6.0 (2019-04-26) installed from CRAN. I tried the method you suggested and still getting following error message:

> BiocManager::install("Rhtslib")
Bioconductor version 3.9 (BiocManager 1.30.4), R 3.6.0 (2019-04-26)
Installing package(s) 'Rhtslib'
trying URL 'https://bioconductor.org/packages/3.9/bioc/src/contrib/Rhtslib_1.16.1.tar.gz'
Content type 'application/x-gzip' length 1470655 bytes (1.4 MB)
==================================================
downloaded 1.4 MB

* installing *source* package ‘Rhtslib’ ...
** using non-staged installation via StagedInstall field
** libs
cd "htslib-1.7" && make -f "/usr/local/Cellar/r/3.6.0_3/lib/R/etc/Makeconf" -f "Makefile.Rhtslib"
Makefile.Rhtslib:130: warning: overriding commands for target `.c.o'
/usr/local/Cellar/r/3.6.0_3/lib/R/etc/Makeconf:167: warning: ignoring old commands for target `.c.o'
clang -g -Wall -O2 -fpic -I.  -c -o kfunc.o kfunc.c
clang -g -Wall -O2 -fpic -I.  -c -o knetfile.o knetfile.c
clang -g -Wall -O2 -fpic -I.  -c -o kstring.o kstring.c
clang -g -Wall -O2 -fpic -I.  -c -o bcf_sr_sort.o bcf_sr_sort.c
clang -g -Wall -O2 -fpic -I.  -c -o bgzf.o bgzf.c
clang -g -Wall -O2 -fpic -I.  -c -o errmod.o errmod.c
clang -g -Wall -O2 -fpic -I.  -c -o faidx.o faidx.c
clang -g -Wall -O2 -fpic -I.  -c -o hfile.o hfile.c
clang -g -Wall -O2 -fpic -I.  -c -o hfile_net.o hfile_net.c
echo '#define HTS_VERSION "1.7"' > version.h
clang -g -Wall -O2 -fpic -I.  -c -o hts.o hts.c
clang -g -Wall -O2 -fpic -I.  -c -o hts_os.o hts_os.c
clang -g -Wall -O2 -fpic -I.  -c -o md5.o md5.c
clang -g -Wall -O2 -fpic -I.  -c -o multipart.o multipart.c
clang -g -Wall -O2 -fpic -I.  -c -o probaln.o probaln.c
clang -g -Wall -O2 -fpic -I.  -c -o realn.o realn.c
clang -g -Wall -O2 -fpic -I.  -c -o regidx.o regidx.c
clang -g -Wall -O2 -fpic -I.  -c -o sam.o sam.c
clang -g -Wall -O2 -fpic -I.  -c -o synced_bcf_reader.o synced_bcf_reader.c
clang -g -Wall -O2 -fpic -I.  -c -o vcf_sweep.o vcf_sweep.c
clang -g -Wall -O2 -fpic -I.  -c -o tbx.o tbx.c
clang -g -Wall -O2 -fpic -I.  -c -o textutils.o textutils.c
clang -g -Wall -O2 -fpic -I.  -c -o thread_pool.o thread_pool.c
clang -g -Wall -O2 -fpic -I.  -c -o vcf.o vcf.c
clang -g -Wall -O2 -fpic -I.  -c -o vcfutils.o vcfutils.c
clang -g -Wall -O2 -fpic -I.  -c -o cram/cram_codecs.o cram/cram_codecs.c
clang -g -Wall -O2 -fpic -I.  -c -o cram/cram_decode.o cram/cram_decode.c
clang -g -Wall -O2 -fpic -I.  -c -o cram/cram_encode.o cram/cram_encode.c
clang -g -Wall -O2 -fpic -I.  -c -o cram/cram_external.o cram/cram_external.c
clang -g -Wall -O2 -fpic -I.  -c -o cram/cram_index.o cram/cram_index.c
clang -g -Wall -O2 -fpic -I.  -c -o cram/cram_io.o cram/cram_io.c
cram/cram_io.c:61:10: fatal error: 'lzma.h' file not found
#include <lzma.h>
         ^~~~~~~~
1 error generated.
make[1]: *** [cram/cram_io.o] Error 1
make: *** [htslib] Error 2
ERROR: compilation failed for package ‘Rhtslib’
* removing ‘/usr/local/lib/R/3.6/site-library/Rhtslib’

The downloaded source packages are in
    ‘/private/var/folders/l7/frxc0f_9639fjgg9g0mc7hz4cxv3nh/T/Rtmptcq3fi/downloaded_packages’
Warning message:
In install.packages(pkgs = doing, lib = lib, repos = repos, ...) :
  installation of package ‘Rhtslib’ had non-zero exit status

Upon trying this a second time I got following error message:

> install.packages("Rhtslib")
Installing package into ‘/usr/local/lib/R/3.6/site-library’
(as ‘lib’ is unspecified)
Warning in install.packages :
  package ‘Rhtslib’ is not available (for R version 3.6.0)