A method for preparing a sequencing library for a plurality of sample polynucleotides in a sample, comprising: a) ligating a single-stranded combo adapter in the form of a plurality of nucleic acid residues to the plurality of sample polynucleotides to produce a plurality of adapter-polynucleotide ligation products, wherein said polynucleotides of said plurality of adapter-polynucleotide ligation products comprise a 5'-proximal segment and a 3'-proximal segment, and wherein at least one of the 5' proximal segment or 3' proximal segment comprises a sequencing adapter; wherein the combo adapter comprises: i) a 5'-proximal segment and a 3'-proximal segment, wherein each proximal segment comprises at least one sequencing adapter, detection sequence, or a combination thereof; ii) 5'-end and 3'-end groups that allow first and second consecutive ligation reactions either directly or after conversion of one or both of these end groups to ligatable 5'-end and 3'-end group(s); and, iii) a template-deficient segment that restricts primer extension by a polymerase over said template-deficient segment; b) circularizing said plurality of adapter-polynucleotide ligation products by ligating their 5' ends to their 3' ends to produce a plurality of circularized adapter-polynucleotide ligation products; c) hybridizing a first primer comprising a sequence at least partially complementary to the 5'-proximal segment of said combo adapter, to said circularized adapter-polynucleotide ligation products; d) extending said first primer with a polymerase to produce a plurality of monomeric nucleic acids, wherein each of the monomeric nucleic acids is complementary to: at least one sample polynucleotide of the plurality of sample polynucleotides flanked by at least a portion of the sequencing adapter; and e) amplifying said plurality of monomeric nucleic acids using said first primer and a second primer, wherein the sequence of the second primer is at least partially complementary to the 3'-proximal segment of said combo adapter, to produce amplicon(s) comprising the sequencing library. a) ligating a single-stranded combo adapter in the form of a plurality of nucleic acid residues to the plurality of sample polynucleotides to produce a plurality of adapter-polynucleotide ligation products, wherein said polynucleotides of said plurality of adapter-polynucleotide ligation products comprise a 5'-proximal segment and a 3'-proximal segment, and wherein at least one of the 5' proximal segment or 3' proximal segment comprises a sequencing adapter; wherein the combo adapter comprises: i) a 5'-proximal segment and a 3'-proximal segment, wherein each proximal segment comprises at least one sequencing adapter, detection sequence, or a combination thereof; ii) 5'-end and 3'-end groups that allow first and second consecutive ligation reactions either directly or after conversion of one or both of these end groups to ligatable 5'-end and 3'-end group(s); and, iii) a template-deficient segment that restricts primer extension by a polymerase over said template-deficient segment; i) a 5'-proximal segment and a 3'-proximal segment, wherein each proximal segment comprises at least one sequencing adapter, detection sequence, or a combination thereof; ii) 5'-end and 3'-end groups that allow first and second consecutive ligation reactions either directly or after conversion of one or both of these end groups to ligatable 5'-end and 3'-end group(s); and, iii) a template-deficient segment that restricts primer extension by a polymerase over said template-deficient segment; b) circularizing said plurality of adapter-polynucleotide ligation products by ligating their 5' ends to their 3' ends to produce a plurality of circularized adapter-polynucleotide ligation products; c) hybridizing a first primer comprising a sequence at least partially complementary to the 5'-proximal segment of said combo adapter, to said circularized adapter-polynucleotide ligation products; d) extending said first primer with a polymerase to produce a plurality of monomeric nucleic acids, wherein each of the monomeric nucleic acids is complementary to: at least one sample polynucleotide of the plurality of sample polynucleotides flanked by at least a portion of the sequencing adapter; and e) amplifying said plurality of monomeric nucleic acids using said first primer and a second primer, wherein the sequence of the second primer is at least partially complementary to the 3'-proximal segment of said combo adapter, to produce amplicon(s) comprising the sequencing library.